Knowledge Base

If a virtual machine that uses an RDM is migrated from an ESX Server 2.x host with VMFS2 datastore to a host running ESX Server 3.0.1 or higher with VMFS3 datastore, a duplicate RDM is created on the destination datastore during the upgrade. The original RDM remains in place on the VMFS2 datastore. This duplication can create issues if two or more virtual machines were sharing the same RDM. After migration, the virtual machines still share the same raw disk, but use different RDMs.

To allow two or more virtual machines to continue to share an RDM, reconfigure them to do so after migrating them to the ESX Server 3.0.1 or higher host and VMFS3 datastore, and delete the extra RDMs created during the virtual machine migrations. After you have completed the migration upgrade, you can delete the original RDM on the VMFS2 datastore if no virtual machines still need it.