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SQL Cluster

By Priya PedamkarPriya Pedamkar

SQL Cluster

Introduction to SQL Cluster

Clusters in standard query language (SQL) databases are collections of multiple physical servers that are grouped together using a LAN connection to create a single database with high availability, less hardware failures, and reduced downtime. A SQL Cluster has single shared disk storage where each physical server can store its database files by using their identical access to it. Each physical server must host an instance of the SQL server. In this article, we will be learning about SQL clusters, their advantages and disadvantages, and methods to create SQL clusters.

Advantages

Some of the advantages are given below:

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  • One of the most important advantages of SQL clusters is that they act as shields to hardware failures. In cases where we have a single database server, the failure in that particular server node leads to a complete halt in the system. But when we have database clusters, this failure can automatically be overcome, by passing over the request to the next available node. This is called a cluster failover.
  • Upgrades on the SQL server service can be performed simultaneously without having to turn off the entire service.
  • Database clusters help in load balancing as each physical node can attend to different batches of service requests.
  • Downtime due to hardware failures are effectively reduced when database clusters are used instead of standalone sql servers.

Disadvantage

Some of the disadvantages are given below:

  • While a very evident disadvantage of database clusters is their inability to recover from database corruption. It is difficult to locate the source of corruption. Also, database clusters have high complexity involved in their design and creation.
  • Database clusters are more expensive compared to standalone SQL servers and their maintenance and administration is more complex and tedious compared to the former.

Having known the advantages and disadvantages of SQL database clusters, let’s go ahead and try to learn how we should install a SQL Server clustered instance. Before proceeding to the step-by-step guide, I will highly encourage you to go through the list of prerequisites for the installation process:

  • Windows PowerShell
  • NET Framework 3.5 SP1
  • Microsoft Update package (required for SQL Server 2019 and above only. Older versions have Microsoft update pre-installed in them)
  • SQL Server Setup support files
  • Do not use unsupported symbols in the cluster name. Some of the unsupported symbols are comparison operators such as (<,>), double and single quotes(“,’), and (&).
  • Configuration of all cluster nodes must be the same
  • SQL Server installation disk should not be encrypted or compressed
  • Check Port, Network, and Firewall Considerations. SQL Server’s network name and IP address should not be used for any other purposes.
  • After installing the operating system and SQL Server instance on each node of the cluster do not forget to configure Microsoft Distributed Transaction Coordinator(MDTC).

How to Install a SQL Server Cluster?

Once we have taken care of all the prerequisites, we are all set to install a SQL server cluster. Here are the steps to it.

  • Step 1: In order to install and configure a SQL server cluster we have to use SQL Server Setup. Download the SQL Server setup from microsoft.com. Next right-click on setup.exe and run the file as “Run as administrator”. A dialog box will appear in front of you. This is the SQL Server Installation Center. Click on the Installation tab and select “New SQL Server failover cluster installation”.
  • Step 2: Enter the product key in the SQL server installation window and click on next.
  • Step 3: After clicking on Next, a new window will appear in front of you. Click on the check box to accept the terms and conditions and finally click on Next.
  • Step 4: On clicking Next, SQL Server will start ensuring whether all the rules and prerequisites have been satisfied. If yes, then the Next button will be enabled and you can proceed ahead by clicking on it. If all the rules are not satisfied, then we have to start again, while ensuring that all the environmental conditions have been satisfied. Also ensure that you are running a 64-bit SQL Server on 64-bit hardware that is running on a 64-bit Windows operating system.
  • Step 5: On the next dialog box, check if you want to receive updates from Microsoft and SQL Server and click on Next.
  • Step 6: After clicking on Next, a failover cluster rules will appear in front of you. A list of both successful and warning rules will be there. Click on Next to go ahead in the installation process.
  • Step 7: Once you will click on the Next, a new dialog box with two options : configure SQL Server feature installation and SQL Server PowerPivot for SharePoint will appear. Choose one as per requirement and click on next.
  • Step 8: The next dialog box for feature selection will appear. Select the required instance and share features based on requirements and click on Next.
  • Step 9: In the next dialog box called instance Configuration window, enter SQL Server Network Name and click on Next.
  • Step 10: On the next dialog box called Cluster resource group, select the name of the cluster group and proceed.
  • Step 11: On the cluster disk selection window, select the disks that you want. Select only shared disks that are part of the current cluster.
  • Step 12: On the cluster network selection, enter a unique and unused ip address for the cluster and click on next.
  • Step 13: Next, enter the SQL Server service accounts and their respective passwords for Server configuration and click on next.
  • Step 14: Next proceed to Data directory configuration. Enter the required details, while ensuring that the path specified for the TempDB data and log files exists on all the cluster nodes. If this is not the case, then SQL Server will fail to come online. Click on Next.
  • Step 15: An alert will come in front of you, click on Yes to complete the installation process.

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