I have 2 zimbra-mta, 2 zimbra-mailbox VMs on vSphere 5. Since both zimbra-mailbox VMs are using raw device mapping, VMware vendor were hesitating to upgrade it's virtual hardware (from version 7)

I believe VM snapshot would fail, but what about other backup solution? I can only think of setting up a temporary Netvault Backup with VMware plugin but not sure if that would work with RDM.