In an environment with storage virtualization devices (SVD), VI Client might incorrectly display RDM LUNs, which are in physical compatibility mode, as available disk in the Add Storage wizard. This situation can potentially cause data to be overwritten.
As a workaround for this issue, you must take special caution to ensure an empty LUN is selected for VMFS volume creation. The following instructions show you how to indentify and compile an RDM-to-LUN mapping list, which you should use to identify LUNs in use so they are not accidentally reused and overwritten.
If the underlying storage of your ESX Server system is virtualized with SVD technology, follow these procedures to recreate the RDM mapping files for the virtual machines. The procedure is broken into two parts:
Perform the following steps after the LUNs have been virtualized and presented to the ESX Server hosts according to the storage vendor's VI3-specific documentation.
Warning: As described in the Details section (above), after you have completed the above steps for all RDMs, LUNs that are already used as RDM might show up as available disk when the Add Storage wizard is launched in the VI Client. If the virtual machine accessing the RDM is in a powered off state, and the RDM LUN is mistakenly selected as the disk for VMFS volume creation, then data loss could occur.
Caution: Always ensure an empty LUN is selected for VMFS volume creation. Prior to selecting the LUN in the wizard, use the LUN-to-RDM correlation list that you compiled in Steps to Perform After LUN Virtualization (above) to verify that the LUN you are going to use is not on the list.