Exchange 2007 has several server roles,
including the mailbox server, edge, hub and client.
Microsoft cluster services (MSCS) can be used to protect the mailbox role using ‘Continuous Cluster Replication’.
The other roles can not be protected by MSCS and hence if one of those nodes fails it can not be recovered.
Running Exchange 2007 on VMware provides a series of HA benefits:
1 – only protection available for edge, hub and client server roles.
2 – can also be used as sole protection for the mailbox role. This eliminates the need to support CCR which is complex and costly to implement. Of course this is only viable if a few minutes of downtime for the mailbox server are acceptable.
3 – Or can be used to complement CCR for the mailbox role when downtime can not be tolerated. CCR includes 2 nodes max. If a node fails, the mailbox is no longer protected. VMware HA can be used to bring up the VM quickly and reinstate the protection.