Exchange CCR cluster on VMware with iSCSI

A few weeks ago I got an assignment to review a colleague’s infrastructure design based on VMware.
The design was fine (because they used my design document as template
) but one thing triggered me.
There was a special port group on one of the virtual switches names ‘MSCLUSTER’. No problem so far but I heard the client recently migrated to iSCSI storage.
The combination Microsoft Clustering Services (MSCS) combined with iSCSI triggered my alarm bells. As I recalled Microsoft Clustering on iSCSI is not a problem but Microsoft Clustering on VMware with iSCSI is not supported (by VMware).
So, I rejected the design based on this support issue.
This message was not well received, as it turned out they had just migrated their clustered Exchange servers and had been running this way for a while now. Proposing to the client to migrate again was no option. So they tried to question my findings. They had been running this setup without any problems and Exchange CCR clustering wasn’t real Microsoft Clustering because no disks were clustered, only the Exchange services.



