Does each instance of SQL Server on a cluster require its own LUN?

Question

I'm setting up a Misc SQL Cluster (Windows 2008/SQL 2005 & 2008) that will be active/active and have about a dozen SQL instances on it. From the documentation I've read, I can't tell if each SQL instance will need its own LUN, or if I can have a single, really big LUN created, and then create a dozen different partitions on that LUN (one for each SQL instance).

In either case, the physical disk layout on the SAN won't change, so it really doesn't matter from a performance standpoint which one I choose (assuming I can choose either). I just want to know if the partition method works, or if each instance needs to own its own LUN to handle the failover properly.

Answer 1

Each instance will need separate disks/LUNs. They will be "owned" by the active node and are a dependent resource.

If you think about it, how can 2 SQL Server instances share a drive? It's a conflict.

Since Windows 2003 you can use NTFS mount points, that is mount a LUN in an empoty folder in a drive. I've not tried it myself though.

Edit: some nice pictures here "How do Cluster Shared Volumes work"

Answer 2

You will need separate disks for each instance. In Server 2008 you will add the shared storage for each instance in the Failover Manager.

Answer 3

I wonder if there is a way to use CSV (Clustered Shared Volumes) to get around this. In Windows 2008 R2 you can set it up so that you can have more than one node in a cluster access the same LUN - no longer do you have to assign a LUN to one node only!!