I have an issue where RDMs disconnected from the Guest OS (in this case, Windows 2008R2 64bit) using SnapDrive 6.3.1 are sometimes not fully removed from the virtual machine. The disk is not visible in the OS or in SnapDrive so appears to have been removed, but going to Edit Settings on the VM will still show the RDM as connected, and the LUN still exists and appears mapped on the filer. I've also noticed when viewing the storage paths on the host a number of 'dead' paths, which I assume are old RDM connections.
This happens on both ESXi4 and ESXi5 hosts.
This can cause problems if a LUN is removed from the filer, as it appears to be no longer connected to the Guest OS, when the VM still thinks it is connected.