Understanding Pod Disruption Budgets and their impact on AKS Cluster Upgrades

AKS Cluster upgrade failed with the Error, listed below..  

Pod eviction operations have failed with Eviction Failure errors. Drain operations are performed when there is a need to safely evict pods from a specific node during operations such as:

• Draining a node for repair or upgrade.
• Cluster autoscaler removing a node from a node pool.
• Deleting a node pool.

During cluster or agent pool upgrades, before a node can be upgraded, its workloads are scheduled onto another node to maintain workload availability.

Drain marks a node as going out of service and as such all of the pods on the node are evicted. The operation periodically retries all failed requests until all pods on the node are terminated, or until a timeout is reached. Drain failures generally indicate a timeout was reached and the pods were not able to be evicted from the node within the timeout period.

The main reasons for a drain failure would be:

• Drain simply took longer than expected.
• Incorrectly configured pod disruption budgets.
• Slow disk attach or detach.

 What is pod disruption budget and how does it impacts AKS cluster upgrade:-

Ans:-

Pod Disruption Budget (PDB) is a Kubernetes feature that allows you to specify the minimum number of pods of a certain type that must be available during a disruption event, such as a node upgrade, a rolling deployment, or a network outage. By setting a PDB, you can ensure that your application remains available and responsive during these events, while minimizing the risk of data loss or downtime.

In an AKS cluster upgrade scenario, PDBs can impact the upgrade process in a few ways. When you upgrade an AKS cluster, the nodes are upgraded one by one, and during the upgrade, the nodes are cordoned off, meaning no new pods can be scheduled on them, and existing pods are gracefully evicted and rescheduled on other nodes.

Here are some ways PDBs can impact AKS cluster upgrades:

Ensuring Availability: If you have a PDB set for a deployment or a StatefulSet, the AKS upgrade process will ensure that the minimum number of pods specified in the PDB is maintained during the upgrade. This ensures that the application remains available during the upgrade, even if some of the nodes are cordoned off or unavailable.

Upgrade Speed: If you have a strict PDB set, the upgrade process may take longer to complete, as the AKS cluster upgrade process will wait until the minimum number of pods specified in the PDB are available on the new nodes before moving on to the next node.

Risk Mitigation: If you do not have a PDB set, or if the PDB is set too low, there is a risk that during the upgrade process, some pods may be evicted or terminated, which can result in data loss or downtime.

Overall, PDBs play an important role in ensuring the availability and stability of applications during AKS cluster upgrades. By setting a PDB, you can minimize the impact of node disruptions and ensure that your application remains available and responsive during the upgrade process.

Q:- How to check how many pod disruption budget are set in your AKS cluster before upgrade:-

Ans:-

kubectl get pdb --all-namespaces

output:-

NAMESPACE       NAME                 MIN AVAILABLE   MAX UNAVAILABLE   ALLOWED DISRUPTIONS   AGE

calico-system   calico-typha         N/A             1                 1                     11d

ingress-basic   my-nginx-pdb         2               N/A               0                     6d1h

kube-system     coredns-pdb          1               N/A               1                     11d

kube-system     konnectivity-agent   1               N/A               1                     11d

kube-system     metrics-server-pdb   1               N/A               1                     11d

rak                       my-app-pdb           3               N/A               0                     6d2h

Explanation:-

The output is showing the Pod Disruption Budgets (PDBs) for various namespaces in the AKS cluster. Each row in the output corresponds to a single PDB and contains the following information:

NAMESPACE: The namespace in which the PDB is defined.

NAME: The name of the PDB.

MIN AVAILABLE: The minimum number of replicas that must be available during a disruption. This is the minimum number of pods that must be running for the PDB to be satisfied.

MAX UNAVAILABLE: The maximum number of replicas that can be unavailable during a disruption. This is the maximum number of pods that can be unavailable for the PDB to be satisfied.

ALLOWED DISRUPTIONS: The total number of allowed disruptions for the PDB.

AGE: The age of the PDB, i.e., the amount of time since it was created.

Let's take an example of the rak namespace and the my-app-pdb PDB. 

It has a minimum availability of 3, which means that during any disruption, at least 3 replicas of the application must be available. The MAX UNAVAILABLE is set to N/A, which means that during a disruption, there can be no more than 0 replicas of the application that can be unavailable. 

The ALLOWED DISRUPTIONS are set to 0, which means that there are no allowed disruptions for this PDB. 

This means that if the AKS cluster upgrade requires a node to be drained, the Kubernetes control plane will ensure that at least 3 replicas of the application are running on other nodes before draining the node with the application pod. 

If there are not enough nodes to maintain the minimum availability, the node will not be drained, and the upgrade will be postponed until enough nodes are available.

for some of pdb like my-nginx-pdb and my-app-pdb, the  Allowed disruption is set to 0. it means 

that no pods can be safely evicted during maintenance or upgrade operations, as any disruption to the pods would result in a violation of the PDB constraints. This can impact the availability and resiliency of the application running on the cluster.

During an AKS cluster upgrade, the upgrade process checks the PDBs to determine if the upgrade can proceed without violating any constraints. If the "Allowed Disruptions" value is set to 0, then the upgrade will not proceed until the PDB constraint is updated or removed.

hence the upgrade will always fail.

Similarly, for the ingress-basic namespace and the my-nginx-pdb PDB, the minimum availability is set to 2, and the maximum unavailability is set to N/A, which means that during a disruption, there can be no more than 0 replicas of the application that can be unavailable. The ALLOWED DISRUPTIONS are set to 0, which means that there are no allowed disruptions for this PDB. This PDB ensures that during an upgrade, at least 2 replicas of the my-nginx application are running at all times.

 If there are not enough nodes to maintain the minimum availability, the upgrade will be postponed until enough nodes are available.

In summary, PDBs are used to ensure high availability of applications during node maintenance, upgrades, and other disruptions. By specifying the minimum and maximum number of replicas that must be available during a disruption, PDBs ensure that applications are always available to users.

Q: What to do if ALLOWED disruptions are set to 0 for pdbs in your AKS Cluster and you are trying to upgrade AKS Cluster

Ans:- The upgrade of AKS Cluster will fail. reason is 

The AKS cluster upgrade process takes into consideration the PDBs defined in the cluster, and if the upgrade process violates any of the PDBs, the upgrade process will fail. The upgrade process ensures that it maintains the minimum number of available replicas specified in the PDB while updating the AKS cluster.

In the output provided, some of the PDBs have a minimum available replica count of 1 or more, while some have a minimum of "N/A." This means that during the AKS cluster upgrade, the upgrade process must ensure that there are at least the specified number of available replicas for those pods, or in the case of "N/A," it will default to ensuring that there is at least one available replica.

How to resolve this error.

1. Before upgrade take a backup of specific PDB whose ALLOWED disruption is set to 0

 kubectl get pdb my-nginx-pdb -n ingress-basic -o yaml > my-nginx-pdb.yaml
 kubectl get pdb my-app-pdb -n rak -o yaml > my-app-pdb.yaml 

2. Delete the PDB

     kubectl delete pdb my-nginx-pdb -n ingress-basic
     kubectl delete pdb my-app-pdb -n rak

3. Perform Version upgrade of AKS

C:\Users\kusha>az aks upgrade --resource-group RGP-USE-AKS-DV --name AKS-USE-AKS-DEV --kubernetes-version 1.26.0

Kubernetes may be unavailable during cluster upgrades.

 Are you sure you want to perform this operation? (y/N): y

Since control-plane-only argument is not specified, this will upgrade the control plane AND all nodepools to version 1.26.0. Continue? (y/N): y

4. Restore  PDB

    kubectl apply -f  my-nginx-pdb.yaml -n ingress-basic 
   kubectl apply -f my-app-pdb -n rak

Thats it..

some objective questions for practice:-

Certainly! I apologize for the confusion. I'll generate a new set of questions without indicating the correct answers. Feel free to go through the quiz, and if you have any questions or need the correct answers, let me know.

**Pod Disruption Budget and AKS Cluster Upgrade Quiz**

1. What is the primary purpose of a Pod Disruption Budget (PDB) in Kubernetes?

   - A. Managing networking configurations during upgrades

   - B. Ensuring availability of pods during disruptions

   - C. Handling persistent storage for applications

   - D. Facilitating communication between nodes

2. How does a Pod Disruption Budget impact the AKS cluster upgrade process?

   - A. Accelerates the upgrade speed

   - B. Has no impact on the upgrade process

   - C. Ensures minimum pod availability during the upgrade

   - D. Manages storage configurations

3. During an AKS cluster upgrade, why might a strict Pod Disruption Budget cause the upgrade process to take longer?

   - A. Due to increased network latency

   - B. Ensuring availability of minimum specified pods

   - C. Facilitating external access to services

   - D. Managing persistent storage volumes

4. What is the role of a Pod Disruption Budget when it comes to risk mitigation during an AKS cluster upgrade?

   - A. Speeding up the upgrade process

   - B. Ensuring maximum pod unavailability

   - C. Minimizing the risk of data loss or downtime

   - D. Facilitating communication between nodes

5. How can you check the number of Pod Disruption Budgets set in your AKS cluster before an upgrade?

   - A. `kubectl get pdbs -A`

   - B. `az aks show-pdbs --resource-group <resource-group> --name <aks-cluster-name>`

   - C. `kubectl get pdb --all-namespaces`

   - D. `aks-pdb check`

6. What information does the output of `kubectl get pdb --all-namespaces` provide about Pod Disruption Budgets in an AKS cluster?

   - A. Network latency details

   - B. Pod unavailability statistics

   - C. PDB constraints and age

   - D. Persistent storage usage

7. In the context of Pod Disruption Budgets, what does "ALLOWED DISRUPTIONS" represent in the output of `kubectl get pdb`?

   - A. Maximum allowed pod disruptions

   - B. The total number of allowed disruptions for the PDB

   - C. Minimum allowed pod disruptions

   - D. Disruptions caused by network failures

8. If the "ALLOWED DISRUPTIONS" for a Pod Disruption Budget is set to 0 during an AKS cluster upgrade, what is the likely impact?

   - A. No impact on the upgrade process

   - B. The upgrade will proceed without considering the PDB

   - C. The upgrade will fail if any pod disruption is required

   - D. The upgrade speed will increase

9. How can you resolve an upgrade failure due to a Pod Disruption Budget with "ALLOWED DISRUPTIONS" set to 0?

   - A. Increase the "ALLOWED DISRUPTIONS" value

   - B. Delete the PDB and perform the upgrade

   - C. Ignore the error and continue with the upgrade

   - D. Reconfigure the PDB during the upgrade

10. What information does the command `kubectl get pdb <pdb-name> -n <namespace> -o yaml` provide, and how is it useful during an AKS upgrade?

   - A. Detailed pod resource utilization

   - B. PDB constraints and age

   - C. Configuration backup of the specified PDB

   - D. Network latency statistics

Ans:- 

**Pod Disruption Budget and AKS Cluster Upgrade Quiz**

1. What is the primary purpose of a Pod Disruption Budget (PDB) in Kubernetes?

   - A. Managing networking configurations during upgrades

   - B. Ensuring availability of pods during disruptions

   - C. Handling persistent storage for applications

   - D. Facilitating communication between nodes

2. How does a Pod Disruption Budget impact the AKS cluster upgrade process?

   - A. Accelerates the upgrade speed

   - B. Has no impact on the upgrade process

   - C. Ensures minimum pod availability during the upgrade 

   - D. Manages storage configurations

3. During an AKS cluster upgrade, why might a strict Pod Disruption Budget cause the upgrade process to take longer?

   - A. Due to increased network latency

   - B. Ensuring availability of minimum specified pods

   - C. Facilitating external access to services

   - D. Managing persistent storage volumes

4. What is the role of a Pod Disruption Budget when it comes to risk mitigation during an AKS cluster upgrade?

   - A. Speeding up the upgrade process

   - B. Ensuring maximum pod unavailability

   - C. Minimizing the risk of data loss or downtime

   - D. Facilitating communication between nodes

5. How can you check the number of Pod Disruption Budgets set in your AKS cluster before an upgrade?

   - A. `kubectl get pdbs -A`

   - B. `az aks show-pdbs --resource-group <resource-group> --name <aks-cluster-name>`

   - C. `kubectl get pdb --all-namespaces

   - D. `aks-pdb check`

6. What information does the output of `kubectl get pdb --all-namespaces` provide about Pod Disruption Budgets in an AKS cluster?

   - A. Network latency details

   - B. Pod unavailability statistics

   - C. PDB constraints and age 

   - D. Persistent storage usage

7. In the context of Pod Disruption Budgets, what does "ALLOWED DISRUPTIONS" represent in the output of `kubectl get pdb`?

   - A. Maximum allowed pod disruptions

   - B. The total number of allowed disruptions for the PDB

   - C. Minimum allowed pod disruptions

   - D. Disruptions caused by network failures

8. If the "ALLOWED DISRUPTIONS" for a Pod Disruption Budget is set to 0 during an AKS cluster upgrade, what is the likely impact?

   - A. No impact on the upgrade process

   - B. The upgrade will proceed without considering the PDB

   - C. The upgrade will fail if any pod disruption is required 

   - D. The upgrade speed will increase

9. How can you resolve an upgrade failure due to a Pod Disruption Budget with "ALLOWED DISRUPTIONS" set to 0?

   - A. Increase the "ALLOWED DISRUPTIONS" value

   - B. Delete the PDB and perform the upgrade 

   - C. Ignore the error and continue with the upgrade

   - D. Reconfigure the PDB during the upgrade

10. What information does the command `kubectl get pdb <pdb-name> -n <namespace> -o yaml` provide, and how is it useful during an AKS upgrade?

   - A. Detailed pod resource utilization

   - B. PDB constraints and age

   - C. Configuration backup of the specified PDB 

   - D. Network latency statistics

---

**Answers:**

       1. B

       2. C

       3. B

       4. C

       5. C

       6. C

       7. B

       8. C

       9. B

      10. C

Q:- Examine the scenario where a Pod Disruption Budget (PDB) has "ALLOWED DISRUPTIONS" set to a value greater than 0. What impact does this have on the AKS cluster upgrade process, and under what circumstances might it be beneficial?

Ans:- 

In a scenario where a Pod Disruption Budget (PDB) has "ALLOWED DISRUPTIONS" set to a value greater than 0 during an AKS cluster upgrade, it signifies a more flexible constraint on pod disruptions. Let's examine the impact and potential benefits:

**Impact on AKS Cluster Upgrade Process:**

1. **Gradual Pod Disruptions:**

   - With "ALLOWED DISRUPTIONS" greater than 0, the AKS upgrade process can gradually disrupt a specified number of pod replicas at a time.

   - Pods are evicted in a controlled manner, allowing the upgrade to progress without waiting for all replicas to be available simultaneously.

2. **Faster Upgrade Process:**

   - The flexibility provided by allowing a certain number of disruptions facilitates a potentially faster upgrade process compared to a PDB with "ALLOWED DISRUPTIONS" set strictly to 0.

   - This is beneficial when there's a need to complete the upgrade within a reasonable timeframe.

3. **Reduced Downtime Risk:**

   - Allowing some disruptions reduces the risk of prolonged downtime during the upgrade.

   - Applications may continue to function with a slightly reduced capacity, minimizing the impact on end-users.

4. **Optimized Resource Utilization:**

   - The AKS upgrade process can optimize resource utilization by evicting pods gradually, ensuring a balanced distribution of workload across available nodes.

**Circumstances in Which it Might be Beneficial:**

1. **Balancing Speed and Availability:**

   - When there's a need to balance the speed of the upgrade with maintaining a reasonable level of availability, setting "ALLOWED DISRUPTIONS" to a value greater than 0 is beneficial.

2. **Resource Constraints:**

   - In scenarios where resource constraints or node capacities may limit the simultaneous rescheduling of pods, allowing controlled disruptions can help manage these limitations.

3. **Applications Tolerant to Disruptions:**

   - For non-critical applications that can tolerate temporary disruptions, setting "ALLOWED DISRUPTIONS" to a higher value can expedite the upgrade without compromising the overall stability.

4. **Phased Rollouts:**

   - When dealing with a large number of replicas or diverse applications, allowing disruptions in phases can be strategically advantageous, preventing potential bottlenecks.

5. **Customized Upgrade Strategies:**

   - For specific applications or services with unique requirements, setting "ALLOWED DISRUPTIONS" provides the flexibility to tailor upgrade strategies according to their specific needs.

In summary, setting "ALLOWED DISRUPTIONS" to a value greater than 0 in a PDB during an AKS cluster upgrade introduces flexibility, allowing for a more balanced trade-off between upgrade speed and maintaining a certain level of availability for applications. This approach is particularly useful in scenarios where a strict constraint on disruptions is not critical, and a faster, more gradual upgrade is desired.

Thanks for reading... 

Troubleshooting Kubernetes ImagePullBackOff Error: Failed to Pull and Unpack Image

 Events:

  Type     Reason     Age                    From               Message

  ----     ------     ----                   ----               -------

  Normal   Scheduled  4m11s                  default-scheduler  Successfully assigned ingress-basic/ingress-nginx-admission-create-ncwjj to aks-nodepool1-27424342-vmss000000

  Normal   Pulling    2m40s (x4 over 4m11s)  kubelet            Pulling image "acruseaksdv.azurecr.io/ingress-nginx/kube-webhook-certgen:v1.1.1"

  Warning  Failed     2m40s (x4 over 4m10s)  kubelet            Failed to pull image "acruseaksdv.azurecr.io/ingress-nginx/kube-webhook-certgen:v1.1.1": rpc error: code = Unknown desc = failed to pull and unpack image "acruseaksdv.azurecr.io/ingress-nginx/kube-webhook-certgen:v1.1.1": failed to resolve reference "acruseaksdv.azurecr.io/ingress-nginx/kube-webhook-certgen:v1.1.1": failed to authorize: failed to fetch anonymous token: unexpected status: 401 Unauthorized

  Warning  Failed     2m40s (x4 over 4m10s)  kubelet            Error: ErrImagePull

  Warning  Failed     2m25s (x6 over 4m9s)   kubelet            Error: ImagePullBackOff

  Normal   BackOff    2m11s (x7 over 4m9s)   kubelet            Back-off pulling image "acruseaksdv.azurecr.io/ingress-nginx/kube-webhook-certgen:v1.1.1"

How to fix this:- 

To resolve this issue, you may want to check the following:

Ensure that the image reference is correct. Verify that the image is available in the specified registry, and that the reference is correct and up to date.

Check the authentication credentials. Ensure that the Kubernetes cluster has the correct credentials to access the Azure Container Registry. You may want to verify the Azure Service Principal credentials and permissions to access the registry.

Check the network connectivity. Verify that the Kubernetes cluster node can access the internet and the Azure Container Registry without any network restrictions.

Check the Kubernetes cluster configuration. Ensure that the Kubernetes cluster is configured correctly to access the Azure Container Registry. You may want to verify the Kubernetes secret and config map settings.

some basic select query practice

 Some basic Select Query Practice

Based on above table structure generate the output of below query.

A.Write a query to retrieve the total number of customers in the Customer table.

B.Write a query to retrieve the addresses of all customers in the CustomerAddress table, along with their corresponding first and last names from the Customer table.

C.Write a query to retrieve the number of customers per country in the Address table, sorted by country name in ascending order.

D.Write a query to retrieve the total number of distinct email addresses in the Customer table.

E.Write a query to retrieve the names and addresses of all customers who live in California.

F.Write a query to retrieve the number of customers who have a password hash value in the Customer table.

G.Write a query to retrieve the first and last names of all customers who have a salesperson assigned to them.

H.Write a query to retrieve the number of unique city names in the Address table.

I.Write a query to retrieve the first and last names of all customers who have a company name assigned to them.

J.Write a query to retrieve the first and last names of all customers who do not have a middle name assigned to them.

Some basic questions on SQL Server Administration

1. How will you check SQL Server is running on which port

There are several ways to check which port SQL Server is running on:

Using SQL Server Configuration Manager: 

Open SQL Server Configuration Manager, 
expand SQL Server Network Configuration, 
select Protocols for [Instance Name], and then check the properties of TCP/IP. 
The port number should be listed under the IPAll section.

Using SQL Server Management Studio: 

• Connect to the SQL Server instance using SQL Server Management Studio, 
• right-click on the server name in Object Explorer,
•  select Properties, and then check the Server Properties > Connections page. 
• The TCP Port value should be listed.

Using T-SQL: Connect to the SQL Server instance using SQL Server Management Studio, open a new query window, and run the following T-SQL command:

SELECT DISTINCT local_tcp_port

FROM sys.dm_exec_connections
WHERE local_tcp_port IS NOT NULL;

This will return the port number that the SQL Server instance is listening on for TCP/IP connections.

Note: If SQL Server is using a dynamic port (i.e. the port is not set to a specific value), then you can check the SQL Server Error Log for the port number. Look for a message that says "Server is listening on [ 'any' <ipv4> <ipv6> <named instance>]." The port number will be listed after the named instance value.

2.How will you check SQL Server  system databases are in which drive

You can check the location of SQL Server system databases by running the following query in SQL Server Management Studio:

SELECT name, physical_name

FROM sys.master_files

WHERE database_id IN (1,2,3,4)

This query will display the names and physical paths of the system databases: master, model, msdb, and tempdb. You can identify the drive by looking at the beginning of the physical path.

3.What are the different version of SQL Server in market

There are several versions of SQL Server currently in the market. 

The most recent version as of my knowledge SQL Server 2019.

 Some of the previous versions include:

SQL Server 2017

SQL Server 2016

SQL Server 2014

SQL Server 2012

SQL Server 2008 R2

SQL Server 2008

SQL Server 2005

Here are the version numbers for the SQL Server versions you mentioned:

SQL Server 2019: 15.x

SQL Server 2017: 14.x

SQL Server 2016: 13.x

SQL Server 2014: 12.x

SQL Server 2012: 11.x

SQL Server 2008 R2: 10.5.x

SQL Server 2008: 10.x

SQL Server 2005: 9.x

4.What are the different type of editions in sql server 2019

SQL Server 2019 offers several editions, each with different feature sets and pricing options. 

The different editions of SQL Server 2019 are:

Express: A free edition limited to one CPU, 1 GB memory usage, and a maximum database size of 10 GB.

Developer: A free edition for development and testing purposes that includes all the features of SQL Server Enterprise Edition.

Standard: An entry-level edition that includes basic features for small to medium-sized businesses.

Enterprise: A high-end edition with advanced features designed for large-scale, mission-critical applications.

Web: A low-cost edition designed for web applications.

Business Intelligence: An edition designed for business intelligence and data warehousing solutions.

Datacenter: An edition designed for highly virtualized datacenter and cloud-based environments.

Note that the availability of these editions may vary depending on the cloud service provider and licensing agreement.

5.How can you check the version of SQL Server Installed on your machine

You can check the version of SQL Server installed on your machine by following these steps:

Open SQL Server Management Studio.

Connect to the SQL Server instance.

In the Object Explorer window, right-click on the server name and select Properties.

In the Server Properties window, select the General tab.

The version information will be displayed under the Product field.

Alternatively, you can also check the version information using a T-SQL query:

SELECT @@VERSION

This will return a resultset that includes the version and edition information.

6.SQL Server supports several network protocols, including:

TCP/IP - This is the most common protocol used for SQL Server communication over a network.

Named Pipes - This protocol is used for communication between processes on the same computer.

Shared Memory - This protocol is used for communication between processes on the same computer.

VIA - This is a high-performance protocol that is used for communication over a high-speed network.

Note that some of these protocols may be disabled by default, and may need to be enabled in SQL Server Configuration Manager before they can be used.

7.How will you remotely check errorlog file of SQL Server

You can remotely check the SQL Server error log file by connecting to the server using SQL Server Configuration manager  or by using Transact-SQL (T-SQL) query.

1. Open SQL Server Configuration Manager.
2. Expand the "SQL Server Services" node and select the SQL Server instance you want to check.
3. Right-click on the instance and select "Properties".
4. In the "SQL Server Properties" window, select the "Advanced" tab.
5. Scroll down to the "Startup Parameters" property and locate the parameter named "-e".
6. The value of the "-e" parameter specifies the location of the SQL Server error log file.

1. Using Transact-SQL (T-SQL) query:

Connect to the SQL Server instance using SSMS or any other client tool.

Open a new query window and execute the following T-SQL command:

EXEC sys.sp_readerrorlog;

This will display the contents of the current SQL Server error log file in the Results pane.

Alternatively, you can use the xp_readerrorlog system stored procedure to read the SQL Server error log file. The syntax for this command is:

xp_readerrorlog [ [ @p1 = ] 'start' ] [ , [ @p2 = ] 'end' ]

[ , [ @p3 = ] { 'string' | spid } ] [ , [ @p4 = ] 'sort_order' ]

Where:

@p1 and @p2 are optional parameters that define the start and end log file number, respectively.

@p3 is an optional parameter that specifies a search string or a SQL Server process ID (spid).

@p4 is an optional parameter that defines the sort order of the results.

For example, to read the error log file and search Recovery keyword for the current SQL Server instance, you can execute the following command:

EXEC xp_readerrorlog 

    0, 

    1, 

    N'Recovery', 

    N'', 

    N'2023-01-01 00:00:01.000', 

    N'2023-12-07 09:00:01.000'

8.How to check which port and protocol is enabled

To check which port and protocol is enabled in SQL Server, you can use the SQL Server Configuration Manager or T-SQL queries. Here are the steps to check the port and protocol settings using both methods:

Using SQL Server Configuration Manager:

1. Open SQL Server Configuration Manager.
2. Expand the "SQL Server Network Configuration" section.
3. Select the SQL Server instance you want to check the settings for.
4. In the right pane, you can see the protocols that are enabled (such as TCP/IP, Named Pipes, etc.).
5. Double-click on the protocol you want to check (for example, TCP/IP).
6. In the Protocol Properties window, select the "IP Addresses" tab.
7. Under the IPAll section, you can see the TCP/IP port number that is being used.

Using T-SQL Queries:

Open SQL Server Management Studio and connect to the SQL Server instance you want to check.

Open a new query window and run the following query:

SELECT 

    DISTINCT protocol_name, 

    local_tcp_port 

FROM 

    sys.dm_exec_connections 

WHERE 

    protocol_name IN ('TCP', 'NP');

This query retrieves information about the protocols that are enabled and the port numbers that are being used. The results will show the protocol name (TCP or Named Pipes) and the local TCP port number that is being used.

Note that the specific steps or query results may vary depending on the version of SQL Server you are using.

Ephemeral storage & Persistent storage in AKS difference and how to expand a PVC from 1 GB to 60 GB

Ephemeral storage 

--------------------------------------

In a Kubernetes cluster, storage can be categorized into two types: ephemeral storage and persistent storage. Ephemeral storage is temporary storage that is tied to the lifecycle of a pod, while persistent storage retains data even when the pod is deleted or restarted.

Ephemeral storage is local to the node where the pod is running. This means that the capacity and availability of ephemeral storage depend on the node's resources. The most common use of ephemeral storage is as a scratch space for temporary files or as a cache. Examples of ephemeral storage include emptyDirs and hostPaths.

EmptyDirs are Kubernetes volumes that are created and destroyed with a pod's lifecycle. When a pod is deleted, its emptyDir is deleted along with it. HostPaths are volumes that are mounted from the host's file system. They are useful for testing, but they have several limitations, such as reduced portability and security risks.

Ephemeral storage is useful for applications that don't require data persistence or for data that can be easily regenerated or recreated. Ephemeral storage is also useful for stateless applications, such as web servers or microservices.

Example  of ephemeral storage 

apiVersion: apps/v1
kind: Deployment
metadata:
  name: webserver-deployment
  namespace: rak
spec:
  replicas: 1
  selector:
    matchLabels:
      app: webserver
  template:
    metadata:
      labels:
        app: webserver
    spec:
      containers:
      - name: webserver
        image: nginx:latest
        ports:
        - containerPort: 80
        volumeMounts:
        - name: html
          mountPath: /usr/share/nginx/html
      volumes:
      - name: html
        emptyDir: {}

---

apiVersion: v1
kind: Service
metadata:
  name: webserver-service
  namespace: rak
spec:
  selector:
    app: webserver
  ports:
  - name: http
    port: 80
    targetPort: 80
  type: LoadBalancer

---

Persistent storage 

-----------------------------------

Persistent storage, on the other hand, retains data even when the pod is deleted or restarted. Persistent storage can be provisioned independently of the nodes and can be scaled up or down as needed. Persistent storage is commonly used for storing application data, databases, and logs.

In AKS, persistent storage can be provided using Azure Disks, Azure Files, or other cloud-based storage solutions. Azure Disks are durable and performant block storage solutions that are optimized for running databases and other I/O intensive workloads. Azure Files are fully managed file shares that can be accessed from anywhere using the SMB protocol.

Persistent storage can be provisioned using PersistentVolumeClaims (PVCs), which are used to request storage from a storage provider. The PVC is a request for a certain amount of storage with a specific storage class. The storage provider provisions the storage, and the PVC is bound to a PersistentVolume (PV). The PV is a representation of a physical volume, such as a disk or a file share, that can be mounted to a pod.

The storage class is used to specify the type of storage that is requested. In AKS, there are several storage classes available, such as standard, premium, and ultra disks. The storage class determines the performance and cost characteristics of the storage.

Persistent storage is useful for applications that require data persistence, such as databases or file shares. Persistent storage is also useful for stateful applications, such as stateful sets or replicated databases.

The choice between ephemeral and persistent storage depends on the application's requirements for data retention, availability, and scalability. Ephemeral storage is useful for applications that don't require data persistence or for data that can be easily regenerated or recreated. Persistent storage is useful for applications that require data persistence and for stateful applications.

In conclusion, ephemeral storage and persistent storage are two types of storage in a Kubernetes cluster. Ephemeral storage is temporary and local to a pod, while persistent storage is durable and independent of a pod's lifecycle. The choice between ephemeral and persistent storage depends on the application's requirements for data retention, availability, and scalability. AKS provides several storage solutions, such as Azure Disks and Azure Files, that can be used to provide persistent storage for Kubernetes workloads.

Example of Persistent Storage

apiVersion: v1

kind: PersistentVolumeClaim

metadata:

  name: html-pvc

  namespace: rak

spec:

  accessModes:

    - ReadWriteOnce

  resources:

    requests:

      storage: 1Gi

---

apiVersion: apps/v1

kind: Deployment

metadata:

  name: webserver-deployment-persist

  namespace: rak

spec:

  replicas: 1

  selector:

    matchLabels:

      app: webserver

  template:

    metadata:

      labels:

        app: webserver

    spec:

      containers:

      - name: webserver

        image: nginx:latest

        ports:

        - containerPort: 80

        volumeMounts:

        - name: html

          mountPath: /usr/share/nginx/html

      volumes:

      - name: html

        persistentVolumeClaim:

          claimName: html-pvc

---

apiVersion: v1

kind: Service

metadata:

  name: webserver-service--persist

  namespace: rak

spec:

  selector:

    app: webserver

  ports:

  - name: http

    port: 80

    targetPort: 80

  type: LoadBalancer

A PV will get created

A PVC will get created

under the default storage class 

1 GB Disk will get created and will appear under Management resource group of AKS.

How to expand the Persistent volume claim for a pod in a deployment

suppose you have a PVC, whose size is 1 GB

C:\Users\kusha>kubectl get pvc -n rak-persist

NAME       STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE

html-pvc   Bound    pvc-889c4819-de22-4d03-b2bf-d4147323de8d   1Gi        RWO            default        53m

PVC is in bound state and it is claimed by PV -->  pvc-889c4819-de22-4d03-b2bf-d4147323de8d

C:\Users\kusha>kubectl get pv

NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM                                           STORAGECLASS   REASON   AGE

pvc-7c018ca6-0075-4b86-bda6-4bc7c50a0225   60Gi       RWO            Delete           Bound    mongodb/mongodb-storage-mongodb-statefulset-0   managed-csi             4d12h

pvc-889c4819-de22-4d03-b2bf-d4147323de8d   1Gi        RWO            Delete           Bound    rak-persist/html-pvc                            default                 55m

Check PVC is used by which POD, in order to validate this you will execute the command 

kubectl describe pvc -n rak-persist

check the value of a column used By 

Used By:       webserver-deployment-persist-86b4975964-cf2z5

now check pod is managed by either deployment/statefulsets

kubectl describe pod webserver-deployment-persist-86b4975964-cf2z5 -n rak-persist

check controlled by column

Controlled By:  ReplicaSet/webserver-deployment-persist-86b4975964

How to check Replicaset is controlled by which deployment 

C:\Users\kusha>kubectl describe replicasets webserver-deployment-persist-86b4975964 -n rak-persist

  Controlled By:  Deployment/webserver-deployment-persist

Now we got deployment who is consuming this PVC

Now Scale down deployment to 0

Scaling down a deployment to 0 means that you want to completely stop the deployment and have no instances running. This can be achieved by adjusting the number of replicas of the deployment to 0.

 The method to scale down a deployment to 0 may differ based on the deployment tool or platform that you are using, but here are some general steps that you can follow:

 Use the appropriate command or interface to access the deployment that you want to scale down.

 Locate the configuration settings for the deployment's replicas.

 Change the number of replicas to 0. This can be done by setting the replicas field to 0 in the deployment configuration file or by using a command such as 

    kubectl scale deployment [deployment-name] --replicas=0 for Kubernetes.

 Save the changes to the configuration file or execute the command to update the deployment's settings.

Wait for the deployment to scale down to 0 instances. 

This may take a few minutes depending on the deployment tool and the size of the deployment.

Once the deployment has been scaled down to 0 instances, the deployment will be completely stopped and no resources will be consumed. 

Keep in mind that if you want to restart the deployment later, you will need to adjust the number of replicas back to a positive value.

Now you have to scale down the deployment 

kubectl scale deployment webserver-deployment-persist --replicas=0

C:\Users\kusha>kubectl scale deployment webserver-deployment-persist --replicas=0 -n rak-persist

deployment.apps/webserver-deployment-persist scaled

C:\Users\kusha>kubectl get pods -n rak-persist

No resources found in rak-persist namespace.

Now expand the PVC

kubectl edit pvc html-pvc   -n rak-persist

expand the storage at 

   

   spec.resources.requests.storage = 60Gi from 1 Gi

and save the file

if you will edit the pvc again, you will get a message like:-

status:

  accessModes:

  - ReadWriteOnce

  capacity:

    storage: 1Gi

  conditions:

  - lastProbeTime: null

    lastTransitionTime: "2023-04-10T03:36:40Z"

    message: Waiting for user to (re-)start a pod to finish file system resize of

      volume on node.

    status: "True"

    type: FileSystemResizePending

  phase: Bound

hence scale up the deployment, so the pod will get created.. 

scale up the deployment

C:\Users\kusha>kubectl scale deployment webserver-deployment-persist --replicas=1 -n rak-persist

deployment.apps/webserver-deployment-persist scaled

C:\Users\kusha>kubectl get pods -n rak-persist

NAME                                            READY   STATUS              RESTARTS   AGE

webserver-deployment-persist-86b4975964-spznk   0/1     ContainerCreating   0          7s

C:\Users\kusha>kubectl get pods -n rak-persist

NAME                                            READY   STATUS    RESTARTS   AGE

webserver-deployment-persist-86b4975964-spznk   1/1     Running   0          49s

Now finally check your PVC expanded or not

C:\Users\kusha>kubectl get pvc -n rak-persist

NAME       STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE

html-pvc   Bound    pvc-889c4819-de22-4d03-b2bf-d4147323de8d   60Gi       RWO            default        88m

Service of type LoadBalancer IP Address will change after AKS Upgrade(yes/no)

Question:- Somebody asked, whether the service of type loadbalancer IPAddress will change when we upgrade AKS Cluster

Ans : No. 

Demo here.. 

C:\Users\kusha>kubectl get services -n rak

NAME                         TYPE           CLUSTER-IP     EXTERNAL-IP      PORT(S)        AGE

webserver-service            LoadBalancer   10.0.217.211   20.242.248.124   80:30326/TCP   34m

webserver-service--persist   LoadBalancer   10.0.202.73    20.120.120.54    80:30085/TCP   21m

az aks show --resource-group RGP-USE-AKS-DV  --name AKS-USE-AKS-DEV  --query "kubernetesVersion" --output table

Result

--------

1.24.9

az aks upgrade --resource-group RGP-USE-AKS-DV --name AKS-USE-AKS-DEV --kubernetes-version 1.25.5

C:\Users\kusha>az aks show --resource-group RGP-USE-AKS-DV  --name AKS-USE-AKS-DEV  --query "kubernetesVersion" --output table

Result

--------

1.25.5

C:\Users\kusha>kubectl get services -n rak

NAME                         TYPE           CLUSTER-IP     EXTERNAL-IP      PORT(S)        AGE

webserver-service            LoadBalancer   10.0.217.211   20.242.248.124   80:30326/TCP   60m

webserver-service--persist   LoadBalancer   10.0.202.73    20.120.120.54    80:30085/TCP   47m

LoadBalacer IP address remains unchanged. 

3-day plan to learn SQL Server 2022 administration basics:

 3-day plan to learn SQL Server 2022 administration basics:

Day 1:

Introduction to SQL Server: Learn about what SQL Server is, its features, and its uses.

SQL Server is a relational database management system (RDBMS) developed by Microsoft. It is used to store, retrieve, and manage data in various applications and websites. Some of the key features of SQL Server include:

High availability: SQL Server provides features such as clustering, mirroring, and replication to ensure high availability and disaster recovery.

Scalability: SQL Server can handle large amounts of data and can scale to meet the needs of growing businesses.

Security: SQL Server has several built-in security features, including encryption, user authentication, and authorization.

Business intelligence: SQL Server provides tools for data analysis, reporting, and integration with other business intelligence applications.

Development tools: SQL Server includes development tools such as SQL Server Management Studio and Visual Studio to help developers manage databases and build applications.

SQL Server is used in a wide range of applications and industries, including finance, healthcare, e-commerce, and government. Its uses include storing and managing data for websites, online transaction processing, business intelligence and analytics, and more.

Installation: Install SQL Server 2022 on your computer and configure the basic settings.

 Create a Windows Azure VM:

a. Log in to the Azure portal at https://portal.azure.com/

b. Click on "Create a resource" and select "Virtual Machine".

c. Choose the appropriate OS version and size for your VM.

d. Configure the other settings such as Networking and Storage as required.

                                                  Virtual Network Settings

 

NSG Settings in Azure

 

e. Click on "Review + Create" and then "Create".

 

Connect to your VM:

a. Once your VM is deployed, click on "Connect".

b. Choose "RDP" as the type of connection and download the RDP file.

c. Use the RDP file to connect to your VM.

 

Download SQL Server 2022:

a. Open a web browser on your VM and navigate to https://www.microsoft.com/en-us/sql-server/sql-server-downloads

b. Choose the appropriate SQL Server 2022 version and edition you want to install, then click on "Download".

 

c. Save the executable file to your local machine.

 

Install SQL Server 2022:

a. Launch the SQL Server 2022 installation executable. Run as Administrator

b. Select "Installation" from the left-hand menu, and then "New SQL Server stand-alone installation or add features to an existing installation".

c. Follow the prompts and select the appropriate installation options as required.

d. Choose the appropriate authentication mode (Windows Authentication or Mixed Mode).

e. Provide the required product key or choose the Evaluation Edition.

f. Specify the installation location, instance name, and other configuration options as required.

g. Continue through the installation process until it completes.

          h. whitelist SQLSERVER.exe on windows firewall.

 using Powershell :-

Open PowerShell as an administrator.

Run the following command to enable script execution: 

  Set-ExecutionPolicy Unrestricted -Scope CurrentUser

Run the following command to add SQLserver.exe to the Windows Defender Firewall Allowed Apps list: 

    New-NetFirewallRule -DisplayName "SQL Server" -Direction Inbound -Program "C:\Program Files\Microsoft SQL Server\MSSQL16.MSSQLSERVER\MSSQL\Binn\sqlservr.exe" -Action Allow -Protocol TCP -LocalAddress Any -LocalPort 1433

Run the following command to add SQLserver.exe to the Windows Defender Firewall Allowed Apps list for the SQL Browser Service:    

New-NetFirewallRule -DisplayName "SQL Browser" -Direction Inbound -Program "C:\Program Files\Microsoft SQL Server\Binn\sqlbrowser.exe" -Action Allow -Protocol TCP -LocalAddress Any -LocalPort 2382

 

Configure SQL Server 2022:

        Download SSMS from below link:-        Download SQL Server Management Studio (SSMS) - SQL Server Management Studio (SSMS) | Microsoft Learn 

a. Open SQL Server Management Studio on your VM.

b. Connect to your instance of SQL Server using the appropriate credentials.

               Local : .\admina

               Remote : SQL Server authentication

SQL Server EXE location:- C:\Program Files\Microsoft SQL Server\MSSQL16.MSSQLSERVER\MSSQL\Binn

SQL Server Errorlog file location:- C:\Program Files\Microsoft SQL Server\MSSQL16.MSSQLSERVER\MSSQL\Log

 

c. Configure your SQL Server instance and databases as required.

 

That's it! You have now installed and configured SQL Server 2022 on a Windows Azure VM.

 

Security: Understand SQL Server security and authentication modes.

SQL Server security and authentication modes are important aspects of database administration. They help protect the database from unauthorized access and ensure that only authorized users can access the database.

SQL Server security modes:

Windows Authentication Mode: In this mode, users are authenticated through Windows Active Directory. This mode is more secure because it uses Windows security features to authenticate users.

Mixed Mode: In this mode, users can authenticate either through Windows Active Directory or through SQL Server authentication. SQL Server authentication requires a username and password and is less secure than Windows authentication.

SQL Server authentication modes:

SQL Server Authentication: This mode requires users to provide a valid SQL Server login and password. This mode is less secure because passwords are stored in the database and can be compromised.

Windows Authentication: This mode allows users to log in using their Windows domain account. This mode is more secure because it uses Windows security features to authenticate users.

In addition to authentication modes, SQL Server provides several security features that can be used to protect the database from unauthorized access:

User Accounts and Logins: SQL Server user accounts are used to authenticate users and provide access to the database. Each user account has a login that is used to connect to the database.

Roles: SQL Server roles are used to group users and assign permissions to the group. Roles can be used to simplify the management of user accounts and permissions.

Permissions: SQL Server permissions are used to control access to the database objects, such as tables, views, and stored procedures. Permissions can be assigned to users or roles.

Encryption: SQL Server provides several encryption features, such as Transparent Data Encryption (TDE), Cell-level Encryption, and Backup Encryption, to protect data at rest and in transit.

Auditing: SQL Server auditing allows the database administrator to monitor and track database activity. Auditing can be used to detect security breaches and identify suspicious activity.

In summary, SQL Server security and authentication modes are critical aspects of database administration. Properly securing the database requires a combination of authentication modes, user accounts, roles, permissions, encryption, and auditing.

Database Creation: Create a new database, configure its settings, and perform basic management tasks.

SQL Server Management Studio: Get familiar with the SQL Server Management Studio tool and its features.

A.What are the prerequisites for installing SQL Server?

1. Hardware requirements: SQL Server has minimum hardware requirements such as CPU, RAM, and disk space. You need to ensure that your hardware meets or exceeds these requirements.
2. Operating system requirements: SQL Server can be installed on various Windows operating systems. You need to make sure that your operating system version is compatible with the version of SQL Server you want to install.
3. .NET Framework: SQL Server requires .NET Framework to be installed on the server. You need to ensure that the correct version of .NET Framework is installed.
4. Windows Installer: SQL Server also requires Windows Installer to be installed on the server. You need to ensure that the correct version of Windows Installer is installed.
5. Windows PowerShell: SQL Server also requires Windows PowerShell to be installed on the server. You need to ensure that the correct version of Windows PowerShell is installed.
6. Internet Information Services (IIS): If you want to install Reporting Services, then IIS is required.
7. SQL Server Native Client: If you want to connect to a SQL Server database from a client computer, then you need to install SQL Server Native Client on the client computer.
8. SQL Server Management Studio (SSMS): SSMS is a tool used to manage and administer SQL Server. It is not a prerequisite for installing SQL Server, but it is recommended that you install it.
9. Firewall: You need to ensure that the firewall settings on the server are configured to allow SQL Server traffic.

Edition and supported feature of SQL Server 2019 :- 

Editions and supported features of SQL Server 2019 - SQL Server | Microsoft Learn

B. What is the difference between a default and named instance of SQL Server?

A default instance is a single instance of SQL Server installed on a server, identified only by the name of the server itself. This is the simplest and most common way to install SQL Server.

A named instance, on the other hand, is a separate instance of SQL Server that can be installed on the same server as the default instance or on a different server.

A named instance is identified by a unique name, and it allows for multiple instances of SQL Server to run on the same machine, each with its own set of databases, logins, and other configuration settings.

One advantage of using named instances is that it allows for better isolation and management of SQL Server instances. It also allows different versions or editions of SQL Server to coexist on the same machine. 
However, managing multiple instances can be more complex and resource-intensive than managing a single default instance.

What authentication modes are available during SQL Server installation?

Windows Authentication mode: With this mode, users are authenticated through the Windows operating system. It allows users to connect to SQL Server with their Windows login credentials, which eliminates the need for a separate login and password for SQL Server.

Mixed mode authentication: This mode allows both Windows Authentication and SQL Server Authentication. With SQL Server Authentication, users are required to provide a separate SQL Server login and password for authentication. This mode is useful when you have SQL Server instances that need to be accessed by users who do not have Windows login credentials.

What is a SQL Server instance ID, and how is it used during installation?

A SQL Server instance ID is a unique identifier assigned to each installation of SQL Server on a computer. During installation, you can specify an instance ID to differentiate between multiple installations of SQL Server on the same computer. This is useful for scenarios where you need to run multiple instances of SQL Server with different configurations or for different applications.

The instance ID is used in various configurations and settings, such as service names, network protocols, and registry keys. For example, the default instance of SQL Server has a service name of "MSSQLSERVER" and a network protocol name of "np:.". A named instance of SQL Server, on the other hand, has a service name in the format "MSSQL$" followed by the instance ID (e.g., "MSSQL$INSTANCE1") and a network protocol name in the format "np:\<computer_name>\pipe\MSSQL$<instance_id>\sql\query".

What are some considerations when deciding on a location for SQL Server installation files and databases?

When deciding on a location for SQL Server installation files and databases, there are several considerations to keep in mind:

Disk Space: SQL Server installation files and databases can take up a significant amount of disk space, so it is important to choose a location with sufficient space available.

Security: The location should be secure to prevent unauthorized access to the installation files and databases.

Performance: The location should be on a disk with good performance characteristics to ensure that the SQL Server instance performs well.

Backup and Recovery: The location should be included in the backup and recovery plan for the SQL Server instance.

Accessibility: The location should be easily accessible to the SQL Server instance and any applications or users that need to access the databases.

Disaster Recovery: The location should be part of the disaster recovery plan for the SQL Server instance, and should be backed up regularly to ensure that data can be restored in the event of a disaster.

What is collation and How do you choose the appropriate collation for your SQL Server installation?

Collation refers to the set of rules that determine how character data is sorted and compared in SQL Server. It includes rules for character set, case sensitivity, accent sensitivity, and other language-specific sorting rules. When installing SQL Server, you need to choose an appropriate collation setting that matches the requirements of your applications and data.

The collation setting can be chosen during SQL Server installation or set for individual databases. There are several factors to consider when choosing a collation, including:

Language: You should choose a collation that matches the language of your data and applications. For example, if you are working with English-language data and applications, you might choose a collation that supports the English language.

Case sensitivity: Collations can be case sensitive or case insensitive. If your application requires case sensitivity, you should choose a case-sensitive collation.

Accent sensitivity: Some languages use accents and other diacritical marks in their characters. If your data and applications require accent sensitivity, you should choose a collation that supports it.

Performance: Some collations perform better than others in certain situations. For example, binary collations can be faster for certain types of queries but may not provide the desired sorting behavior.

In general, it is recommended to choose a collation that supports the language of your data and applications, is case-insensitive, and is accent-insensitive unless your specific requirements dictate otherwise.

What are the different SQL Server components that can be installed, and what are their purposes?

There are several SQL Server components that can be installed, each serving a specific purpose. Some of the commonly used components are:

Database Engine: This is the core component of SQL Server that stores, processes, and manages data.

Analysis Services: This component allows you to create and manage OLAP (Online Analytical Processing) cubes and data mining models.

Reporting Services: This component allows you to create, manage, and deploy reports.

Integration Services: This component is used for data integration and transformation, allowing you to extract data from various sources, transform it, and load it into a destination system.

Master Data Services: This component provides a centralized location for managing master data and ensures its consistency across different applications and systems.

Data Quality Services: This component provides data cleansing and matching capabilities, helping to ensure data accuracy and consistency.

SQL Server Management Studio: This is a graphical user interface tool used to manage and administer SQL Server instances, databases, and other components.

When installing SQL Server, you can choose to install any combination of these components based on your requirements.

What is the purpose of the SQL Server Browser service, and is it required for all installations?

The SQL Server Browser service is responsible for providing information about SQL Server instances installed on a network. When a client application tries to connect to a SQL Server instance, the SQL Server Browser service listens on UDP port 1434 and provides information about the instance to the client.

The SQL Server Browser service is not required for all installations, but it is necessary when installing a named instance of SQL Server or when configuring a server to use dynamic ports. Without the SQL Server Browser service, clients would need to know the port number of the instance they are trying to connect to, which can be difficult to manage in large environments with multiple instances.

However, the SQL Server Browser service does pose a security risk as it can potentially expose information about SQL Server instances to unauthorized clients. It is recommended to disable the SQL Server Browser service if it is not needed or to configure firewalls to restrict access to the service.

SQl Server browser service works on which port

  The SQL Server Browser service listens on UDP port 1434 by default.

How do you configure SQL Server network settings during installation, and what are some considerations for doing so?

During SQL Server installation, network settings can be configured on the "Server Configuration" page. The following are some considerations for configuring these settings:

Protocol: SQL Server supports several network protocols such as TCP/IP, Named Pipes, and Shared Memory. The selection of the protocol depends on the environment and requirements of the application.

IP Address: If SQL Server is being installed on a machine with multiple network cards, the IP address on which SQL Server listens should be specified. This can help in avoiding potential IP conflicts.

Port Number: By default, SQL Server uses port number 1433. However, if required, the port number can be changed during installation to avoid conflicts with other applications.

Authentication Mode: Authentication mode specifies the type of authentication used to connect to SQL Server. SQL Server supports two authentication modes: Windows Authentication and SQL Server Authentication.

Firewall Settings: The firewall settings should be configured to allow incoming connections to SQL Server from client machines. The ports used by SQL Server should be opened in the firewall.

Encryption: SSL encryption can be enabled during installation to ensure that all data transferred between SQL Server and client machines is encrypted.

Named Instances: For named instances, a unique port number is assigned automatically during installation. The port number is registered with SQL Server Browser service, which enables client applications to locate the named instance.

In summary, network settings during SQL Server installation should be configured based on the environment and application requirements. It is essential to consider security, firewall, and encryption settings to ensure that the SQL Server instance is accessible and secure.

Day 2:

Backup and Recovery: Learn how to back up and restore a SQL Server database, and how to configure backup options.

Maintenance Plans: Understand how to create and manage maintenance plans in SQL Server.

Query Optimization: Learn how to optimize SQL Server queries for performance and efficiency.

Indexes: Understand how to create and manage indexes in SQL Server.

SQL Server Agent: Get familiar with the SQL Server Agent tool and its features.

Day 3:

High Availability and Disaster Recovery: Learn about SQL Server high availability and disaster recovery solutions, such as Always On Availability Groups and Failover Clustering.

Monitoring and Troubleshooting: Learn how to monitor and troubleshoot SQL Server performance issues.

Reporting: Get familiar with SQL Server reporting services and how to create and manage reports.

SQL Server Integration Services (SSIS): Understand the basics of SQL Server Integration Services and how to create simple ETL processes.

Advanced Topics: If time allows, explore advanced topics such as SQL Server Analysis Services (SSAS) and SQL Server Reporting Services (SSRS).

Remember to practice what you learn by creating and managing your own SQL Server databases, and by experimenting with different features and settings.

Difference between Deployment and Statefulset

What is difference between deployment and Statefulset 

Deployment:

A deployment is used to manage the deployment and scaling of a set of replicas of a stateless application. A stateless application is one that does not maintain any form of state and can run in any instance or replica. A deployment creates a set of pods (which are the smallest deployable units in Kubernetes) and manages their lifecycle. Deployments are useful when you want to update your application with new code, scale up or down, and maintain a consistent state.

When you create a deployment in AKS, you specify the desired number of replicas, the Docker image to use, and the resources (CPU and memory) required by each pod. AKS creates a set of identical pods, monitors their health, and automatically replaces failed or unresponsive pods with new ones. Deployments also support rolling updates, which allows you to update your application with zero downtime. Rolling updates take place by gradually replacing old pods with new ones.

StatefulSet:

A StatefulSet, on the other hand, is used to manage the deployment and scaling of a set of replicas of a stateful application. A stateful application is one that requires some form of persistent storage, such as a database, and each instance or replica of the application needs to have a unique identity.

When you create a StatefulSet in AKS, you specify the number of replicas, the Docker image to use, the storage requirements, and the unique identity of each replica. AKS creates a set of identical pods with unique identities and persistent storage.

 When a pod is created, it gets a unique hostname and identity that can be used to access its storage. StatefulSets ensure that pods are created in a specific order, and they are terminated in reverse order. This ensures that the stateful application is started and stopped correctly and avoids data loss.

StatefulSets are useful when you have stateful applications that require unique identities and persistent storage. Examples include databases, messaging systems, and file servers. StatefulSets make it easy to scale up or down your stateful applications, and they support rolling updates to update your application with zero downtime.

Example of installing mongodb with statefulset using static storage account

# Set variables
namespace=mongodb
statefulsetname=mongodb-statefulset
storagename=mongodb-storage
storageclass=azure-disk
replicas=1
mongodbusername=admina
mongodbpassword=Password@123

cat <<EOF | kubectl apply -f -
# Create a Namespace mongodb-namespace
apiVersion: v1
kind: Namespace
metadata:
  name: $namespace
EOF

cat <<EOF | kubectl apply -f -
kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: $storageclass
  namespace: $namespace 
provisioner: kubernetes.io/azure-disk
parameters:
  storageaccounttype: Standard_LRS
  kind: Managed
EOF


  

# Create MongoDB StatefulSet
cat <<EOF | kubectl apply -f -
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: $statefulsetname
  namespace: $namespace
spec:
  serviceName: $statefulsetname
  replicas: $replicas
  selector:
    matchLabels:
      app: mongodb
  template:
    metadata:
      labels:
        app: mongodb
    spec:
      containers:
      - name: mongodb
        image: mongo:latest
        env:
        - name: MONGO_INITDB_ROOT_USERNAME
          value: $mongodbusername
        - name: MONGO_INITDB_ROOT_PASSWORD
          value: $mongodbpassword
        ports:
        - containerPort: 27017
        volumeMounts:
        - name: $storagename
          mountPath: /data/db
  volumeClaimTemplates:
  - metadata:
      name: $storagename
    spec:
      storageClassName: $storageclass
      accessModes:
      - ReadWriteOnce
      resources:
        requests:
          storage: 5Gi
EOF

# Create MongoDB StatefulSet explanation

This is a Kubernetes YAML file that creates a StatefulSet to run MongoDB in a Kubernetes cluster. A StatefulSet is a Kubernetes object that provides guarantees about the ordering and uniqueness of pods in a Kubernetes cluster. MongoDB is a popular NoSQL database management system.

The YAML file specifies the following attributes for the StatefulSet:

Name: The name of the StatefulSet, which is provided as a parameter to the script.

Namespace: The namespace where the StatefulSet will be created, which is also provided as a parameter.

Service name: The name of the service associated with the StatefulSet, which is the same as the StatefulSet name.

Replicas: The number of replicas of MongoDB that will be created in the StatefulSet, which is also provided as a parameter.

Selector: The labels used to identify the MongoDB pods managed by the StatefulSet.

Template: The pod template used to create MongoDB pods in the StatefulSet. It contains the following:

 Labels: Used to identify the pods created by the StatefulSet.

 Containers: The container specification for MongoDB, which includes the following:

   Name: The name of the container.

   Image: The MongoDB Docker image to use.

  Env: The environment variables to set in the container, which includes the MongoDB root username and password.

  Ports: The port used by MongoDB.

  VolumeMounts: The storage volume to mount to store MongoDB data.

VolumeClaimTemplates: The storage volume template used to create persistent volumes for MongoDB data. It contains the following:

 Metadata: The name of the volume to be created.

 Spec: The specification of the storage volume, which includes the storage class, access modes, and storage requests.

Overall, this YAML file creates a scalable and persistent MongoDB deployment in a Kubernetes cluster, with authentication enabled using a root username and password, and 5GB of storage allocated for each MongoDB pod.

# Create MongoDB Headless service
cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Service
metadata:
  name: $statefulsetname
  namespace: $namespace
  labels:
    name: mongo
spec:
  ports:
  - port: 27017
    targetPort: 27017
  clusterIP: None
  selector:
    app: mongodb
EOF

Q:- why we create a headless service 

Ans:-why we create a headless service in statefulsets

In a StatefulSet, each pod has a unique and stable hostname that is based on the StatefulSet name and the ordinal index of the pod. For example, a StatefulSet with a name of "mongodb" and replicas set to 3 would create pods with hostnames "mongodb-0", "mongodb-1", and "mongodb-2". This allows applications running inside the pod to use the hostname to connect to other pods in the StatefulSet, rather than relying on IP addresses that may change if pods are added or removed.

By default, Kubernetes creates a cluster IP service for a StatefulSet, which forwards traffic to the pods using their stable hostnames. However, in some cases, it may be useful to have direct access to each pod's hostname, without going through the service. This is where headless services come in.

A headless service is a Kubernetes service that is created with the "clusterIP: None" option. This means that the service does not have a virtual IP address, and instead returns the DNS name of each pod that matches the service selector. In the case of a StatefulSet, a headless service returns the stable hostnames of each pod in the StatefulSet, allowing applications to connect directly to each pod.

There are several reasons why a headless service may be useful in a StatefulSet:

Load balancing: A headless service allows applications to connect directly to each pod, which can be useful for load balancing or distributing workloads across multiple pods.

Stateful application requirements: Some stateful applications require direct access to each pod's hostname in order to function properly.

Database sharding: In databases that support sharding, a headless service can be used to shard data across multiple pods based on their stable hostnames.

Overall, a headless service in a StatefulSet allows for more direct and fine-grained control over how applications connect to pods, and can be useful in a variety of scenarios.

Q:- what if i set replicaset to 3, will  this static storageClass support  replicaset to 3. if not how can we change replicaset to 3. 

ANS:--- ???