I'm setting up a Hyper-V Cluster with two nodes in a workgroup configuration for 2025, and I'm transitioning from VMware, which is a bit easier. Since my hosts aren't joined to an Active Directory, I'll need a Disk or Cloud witness; in this case, it will be a Disk witness. I've already configured a Cluster Shared Volume (CSV) on the Fibre Channel SAN for VM storage. My question is, can the SAN itself also serve as the disk witness, or do I need a separate box for that? If I need a separate setup, I'm assuming I'll require a second volume on the SAN, right? I realize this might not be best practice, but I'm kind of pressed to make it work.
3 Answers
Using the SAN for the disk witness can lead to issues, especially if it fails. It could put your cluster nodes in a split-brain scenario. If you have another device available, a network share is preferable, but it’s definitely not supported in your setup since it must be either a disk or cloud.
Absolutely, you need another LUN for the disk witness. It can be quite small, like around 1GB. This is a standard option when you're adding the CSV in the Failover Cluster Manager.
You do need a separate small LUN for the disk witness, but it can still be on the same SAN as your VMs. Just make sure it's distinct to avoid conflicts.
That’s exactly the reassurance I needed! Thanks for clarifying!
In this case, if the SAN goes down, everything goes down anyway, so I'd prefer to deal with that over a network share, which isn't supported. I could even consider using an iSCSI LUN on my Synology, although that has its drawbacks since that device should primarily serve as backup.