Introduction

Failover cluster in SQL Server is a type of cluster in which two or more independent servers are interconnected with each other via means of physical cables and software. The servers in failover type of clustering are referred to as nodes. This has a major advantage of providing availability of applications and services. If one of the nodes of cluster fails then another node provides the same service.

Requirements for SQL Server Failover Cluster Configuration

The failover cluster configuration requires following necessities:

1. Hardware Requirements
2. Software Requirements
3. Network Infrastructure with domain account requirements

Hardware Requirements- User requires following hardware for failover configuration in SQL Server.

• Server: Since clustering is all about interconnected nodes, therefore we require a set of computers that consists of similar components
• Network Communication Means: For cluster formation, the network adapters and cables are required for connecting the servers/nodes with each other and these connections should be dedicated to network communication.
• Device Controllers for Storage
1. For Serial Attached SCSI: If users are using fiber channels or serial attached SCSI then all the components of storage stack must be same like multipath Input Output and Device Specific Module components must be identical.
2. For iSCSI: If the user is using Internet Small Computer System Interface (iSCSI) then each server should be dedicated to storage and should not be used for network communication.
• Storage: Shared storage is compatible with SQL Server in failover clustering. Storage requirements include the following measures:
1. Use basic disks for failover clustering
2. The partition of each server’s disk done must be with NTFS.
3. Master Boot Record or GUID partition table can be used for partitioning style of disk

Note: The copy of the cluster configuration database is held by a disk in clustered storage and this disk is known as disk witness.

• Deploying SAN with failover configuration: When activating a storage area network (SAN) with a failover cluster follow below mentioned guidelines:
1. Confirming Storage Compatibility: Recheck from the vendors or manufacturers about drivers, firmware, and software (used for storage) whether they are compatible with failover clusters or not.
2. Keep apart storage devices: The servers from different clusters must be unable to access the common storage devices. Generally, a unique Logical Unit Number is used for one set of cluster servers that should be separated.
3. Prefer Using multipath I/O: The hardware vendor should supply a multipath Input-Output device for failover clustering.

Software Requirements- While configuring failover clustering in SQL Server the servers must either run processor supporting 64-bit operating system or Itanium architecture based versions of SQL Server. All the connected servers must have the identical same software updates along with their service packs.

The feature of failover clustering is updated in server products like Windows Server 2008 R2 Enterprise and Windows Server 2008 R2 Datacenter but not in Windows Server 2008 R2 Standard or Windows Web Server 2008 R2.

Network Infrastructure with Domain Account Requirements- Following network infrastructure is used for SQL Server failover cluster configuration.

• IP Address and Network Settings: Ensure at the time of adapter installation that no settings are in conflict. Remember that each adapter must have a unique IP address even if they have identical physical network
• Domain Name System: For naming resolution, the server in the cluster must be DNS.
• Account Administering: At the time of creation of SQL Server cluster, user must be logged on domain with account that has administrator rights and permissions on every servers of the cluster. It can be Domain Users account that is in Administrators collection on each node.
• Domain Role: All the nodes of clusters must be in same Active directory domain, possibly all nodes should have the same domain.
• Clients: As such, no technical expertise required apart from connectors who connect the server for clustering and run softwares that are compatible with services.

Steps to Configuring Failover Clustering in SQL Server:

Follow the given steps for performing the SQL Server failover cluster configuration:

1. Go to Administrative Tool >> Server Manager
2. On each node of the cluster, enable ‘Failure Cluster Feature’ in all servers
3. Click on Next >> Install and then on one of the cluster perform further steps
4. Open Failover Cluster Management from Start >> Administrative Tool >> Failover Cluster Management
5. On the window appearing, on the LHS of window you’ll find Failover Cluster Management there you right click on that and then select Validate a configuration
6. Now Validate a Configuration Wizard window will display on that Enter name and Selected Server and click on Next
7. Now choose Run all tests and then click Next
8. Now a confirmation window appears displaying all the nodes that are connected to that particular node. Validate the information displayed on that screen
9. Now again click on Next and then Finish.

Conclusion

We can configure failover cluster in SQL server at the time of setup installation also otherwise if necessity is after installation the article guides you for such.