When using VMs in a MSCS cluster across box (CAB), you will need to setup the RDMs in a physical compatibility mode and enable bus sharing. Please note that VMs with RDMs in physical mode will not allow you to snapshot either. Basically, you will find that your MSCS VMs will have their snapshot option greyed out. What does this mean?
You can’t use VCB to backup your VMs as that relies on snapshots.
You can’t use vDR for backups as that relies on snapshots.
And lastly you can’t leverage the snapshotting ability for tasks like patching of your VM if you have been practicing that in the past.
When running the disk in independent/persistent mode, you would think that snapshots would still work and only snapshot the vmdk running the OS partition and not your RDM. However, with the bus sharing in place for MSCS to work, the snapshotting criterion is not met. Hence the option remains greyed out. Also, lets assume you are able to snapshot the VM somehow, and you take the snapshot of VM1, after keeping it for a day you suddenly decide to revert it back, I am not sure on how VM2 or even the cluster itself will behave when all of a sudden one of its nodes has forgotten what happened 24 hours ago. So, just don’t snapshot it even if you come up with a way of being able to do it.
One thing I haven’t tried yet is to see what happens when I turn a node off, snapshot it, do what I need to do and when I need to revert, turn it off and then revert. Not sure if this is even possible or supported. Not to mention, the bus sharing will be have to be disabled. But in all seriousness, I would never do this in a production environment. If I ever decide to test this, this will only be for my own curiosity.
Not being able to snapshot should not really be the reason for you to scrap MSCS in VMware. This is simply a limitation to understand prior to designing a solution. If snapshotting is of paramount importance, then this may not be your cup of tea, however will the alternate solution give you that ability? If not being able to back up the VM using VCB or vDR is your issue, then please be informed that you can still backup the VM by installing the agent inside the guest and use a traditional backup mechanism. Leverage the same infrastructure that has been backing up your physical world. MSCS in VMware is not perfect, but it will get there.