Change Block Tracking and virtual-mode RDMs

Does anyone know if Change Block Tracking works properly with virtual-mode RDMs in vSphere 4.1?


I use vCenter 4.1 to manage a 2 host 4.1 cluster that is attached via iSCSI to a NetApp SAN. I'm attempting to use BackupExec 2010 R2 with the Agent for VMware Virtual Infrastructure to perform a policy-based full SAN-based backup weekly with SAN-based differential backups during the weekdays.

My weekly Full backups are now running properly using my Disk-to-Disk-toTape policy(about 760GB total size), but I'm having issues with the daily Differential D2D2T portion. My differential backups are consuming about 570GB of space, which is not right. I'm still tracking down the root cause, but one thing that stands out is a 500GB virtual-mode RDM. When I look at the primary DataStore of this VM I can see the RDM mapping and the associated CTK file (the RDM is DirDB_2.vmdk in the attached screenshot), which tells me that vSphere appears to be doing CBT on the RDM.

However, I've read in other places that vSphere doesn't support CBT on any type of RDM, including virtual-mode. Also the BackupExec VMware Agent FAQ (attached, page 14) states that Backup Exec 2010 doesn't support differential or incremental backups of vRDMs and will only do a full backup.

I've searched quite a bit on this and have an open post on SymConnect, but not a case yet. Also I noticed on Veeam's forums that Veeam 4.0 wouldn't do CBT on vRDMs, but Veeam 4.1 is supposed to.

Can anyone verify whether CBT is fully supported for vRDMs on vSphere 4.1? It would help my case with Symantec if I knew for sure.


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Looking at the vcb_vsphere_backup.pdf , only physical mode RDM's are not supported. See page 23.


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