Before you install and configure your clusters, it is important to understand the concepts of Active/Standby configuration, and how multiple instances can be set up in a SQL configuration.
A configuration is Active/Standby when there is only one master database for each SQL Server, and it is located on a shared or replicated volume. The services run on only one system at a time. The servers are assigned priorities within LifeKeeper for Windows which determine the order of failover for a particular hierarchy.
The figure below depicts a single SQL instance installed on a pair of servers. The instance contains two databases, databaseK and databaseX residing on separate volumes. Note that there is a single master database which resides on shared volume X.
When you create the SQL hierarchy within LifeKeeper for Windows, you are asked to specify the SQL instance to be protected, and the IP resource that will be used to connect to the database. LifeKeeper for Windows then reads the configuration data for that instance and pulls the associated volumes into the hierarchy.
Once the hierarchy is created, it will appear as follows in the LifeKeeper GUI.
In the event of failure, LifeKeeper for Windows brings the SQL Server hierarchy In Service on the backup Server. SQL Server is started on the backup server and it takes over protection of all defined databases as depicted in the figure below.
Multiple SQL Instances
SQL Server can be installed multiple times, which creates multiple SQL instances. LifeKeeper for Windows can protect multiple instances of SQL Server. LifeKeeper for Windows identifies each instance by the unique name given during SQL installation.
One SQL instance may contain multiple SQL databases. Each instance is protected in a single LifeKeeper for Windows hierarchy. Thus, if the SQL instance contains two databases, the corresponding LifeKeeper for Windows hierarchy will protect two databases (along with the associated IP and volume resources).
The figure below depicts three SQL instances: SQLServer (the default instance), SQL2, and SQL3. These are installed on a pair of servers, MILES and DAVIS.
- The databases are located on three different shared storage volumes, K, X and Y. Note that the default instance contains two databases and the other two instances contain one database each.
- Each server can be the primary and backup server for multiple instances.
- It would be possible for MILES to be the primary server for the default instance and DAVIS to be the primary server for the SQL2 and SQL3 instance.
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