Microsoft Cluster Service (MSCS) support on VMware vSphere

Microsoft Cluster Service (MSCS) is Microsoft cluster technology required shared storage supporting SCSI reservation mechanism. Microsoft has introduced new - perhaps more modern and more descriptive - name for the same technology. New name is "Microsoft Failover Cluster" so don't be confused with different names.

VMware has supplementary documentation called "Setup for Failover Clustering and Microsoft Cluster Service" covering the subject. Here is online documentation for vSphere 5.5 and here for vSphere 5.1. This documentation is a must to read to fully understand what is and what is not possible.

However documentation is relatively old so if you want to know up-to-date information you have to leverage VMware KB. Here are two KB articles related to the topic

• Microsoft Cluster Service (MSCS) support on ESXi/ESX (1004617)
• Microsoft Clustering on VMware vSphere: Guidelines for supported configurations (1037959)

And here is general advice.
Plan, plan, plan ... design ... review ... implement ... verify.
I hope you know what I mean.

Microsoft Clustering on VMware vSphere: Guidelines for Supported Configurations

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1037959

MSCS RDMs causing long boot of ESX

That's because RDM LUN attached to MSCS cluster has permanent SCSI reservation initiated by active node of cluster.

In ESX 5 you have to mark all such LUNs as perennially reserved and your ESX boot can be fast as usual.

Here is CLI command to mark LUN
esxcli storage core device setconfig -d naa.id --perennially-reserved=true

This has to be changed on all ESX hosts with visibility to the LUN.

More info at http://kb.vmware.com/kb/1016106