I've read the most recent Microsoft SQL Server and SnapManager for SQL on NetApp Storage Best Practices Guide (TR-4003), but am still unclear of the the Netapp Volume and VM Datastore configuration for SQL Server VM's using VMDK's. The question is:
Should we create a separate Netapp Volume for each SQL Server VM (apx. 20 VM’s), then place all the Database VMDK’s for each SQL Server into these dedicated Volumes/Datastores?
There seem to be some conflicting limitations on the VM and Netapp side that have made this a more difficult decision:
Since we use NFS on our VM hosts, each Netapp Volume will correspond to a single datastore. A VM host (or cluster) is limited to a maximum of 64 datastores, so 20 volumes/datastores would consume a large portion of the maximum limit.
If we mix the VMDK's for several SQL Servers into a single Datastore, then we will need to offset the snapshot schedules for those SQL Servers, so they do not conflict with each other.
Since there is a maximum of 255 snapshots per Volume, having multiple SQL Servers in a single Volume/Datastore would mean we would need to schedule fewer snapshots per SQL Server or a have a shorter snapshot retention period.
How many SQL Server instances are you planning to run per VM? The restriction with 64 datastores is gone with ESX 5.0 .So there is a more headroom for drawing the layout architecture.This is not a hard and fast rule to have a datastore dedicated to a single SQL VM .
You can still have multiple datastores for a single VM if there are high number of SQL instances running per VM.