Cluster Shared Volumes

Edwin Sarmiento discusses Cluster Shared Volumes within Failover Cluster Instances:

CSVs still use the concept of a shared disk but with an added layer of abstraction. Instead of having the shared disk be accessible to only one WSFC node at a time, all of the WSFC nodes have their own logical paths to it. This is made possible thru the Server Message Block (SMB) protocol. Since the WSFC nodes are connected to each other thru the heartbeat network (it’s another reason to have a dedicated network for inter-node communication,) CSV can take advantage of this route to the shared storage to send I/O commands.

Don’t be confused. While all of the WSFC nodes have both physical and logical paths to the shared disk, only the node that owns the SQL Server clustered resource can own it, just like when using traditional shared disks. In other words, the owner node dictates how to send the I/O commands – either directly thru its own access path or thru the heartbeat network. This is why you won’t see any direct dependency on the shared disk if you look at the Dependency Report. It also means that the failover process will be faster with CSVs.

If you’re using SQL Server 2014 or later and have built a cluster, check this feature out and see if it fits in your environment.

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