Networker, VADP and the RDMs in virtual mode

Question

Hello,

I have several doubts about backing up VMs with RDMs through the VADP:

1. Do you know of any VADP limitations regarding RDMs in virtual mode?

2. Assume I have already backed up a VM. The VM was having OS disk on a regular VMFS volume and several big (~2TB) RDMs in virtual mode. How do I restore such a VM? Do I need multiple or a single VMFS volume (a huge one) as a target for this VM to do a restore or is there any way to restore to RDM's (all in virtual mode) directly? Please assume I do not want to overwite my original VM.

Regarding VADP and RDMs in physical mode I found out that:

- VADP cannot be used to protect pass-through disks (RDM: raw device mapped disks in physical compatibility mode)

also:

- VADP cannot be used to protect network mounts (CIFS or NFS) within guest (which is rather obvious)

Regards,

S.

ecarter11 · Accepted Answer

Hello - a similar question was asked recently and this was the answer:

VADP Backup of the data residing within RDM is supported only if it’s a “virtual compatibility” RDM.

For single file restore, it is supported for “virtual compatibility” RDMs as long as the RDM has a NTFS drive letter associated with it.

For DR, the “virtual compatibility” RDM gets converted into regular VMDK during restore, hence care needs to be taken during DR to assign a datastore which has enough space to accommodate the total size of the RDM disk (see page 62 of release notes). Once restored as VMDK, the disk can be converted back into an RDM using vmkfstools command from within ESX/ESXi. Refer below VMware article for more details.

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=3443266

VADP Backup of the data residing within “physical compatibility” RDM is not supported since VMware does not allow snapshots of such RDM disks.

If using “physical compatibility” RDMs, recommended option is to either use traditional guest approach to backup from within guest or go with storage array snapshot feature.

Does this help?

oczkov · Answer

Eric,

Thanks for posting this. It actually answers my main question.

I have a Linux VM (SLES 11 SP1 64-bit) with RDMs in virtual compatibility mode. It's now clear we will need to restore them to a multiple VMFS datastores or one, single big datastore (this would imply using VMFS extents in our case since we've got several 2TB RDMs in the original VM). Converting .vmdk's back into RDMs is strightforward and easy, but it is another step which will consume lots of time during recovery so I am thinking of staying with VMFS and not implementing RDMs at all.

Does anybody know whether VADP restore allows to use different (multiple) datastores - just to place each big .vmdk file on a different datastore or you must point to a single datastore for the whole restore operation?

Regards,

S.

ecarter11 · Answer

Hi - I think the answer to your question can be found in this integration guide (can you get to it?)

http://powerlink.emc.com/km/live1/en_US/Offering_Technical/Technical_Documentation/300-011-693.pdf

Here is what I see:

Pg 56:

The virtual machine can recover to the same VMware ESX server or VMware

vCenter (VC) taken at the time of backup or to a different ESX or VC. Recovery to

different resource pools and different datastores are also supported. A different

datastore can be specified for each disk and a configuration datastore can be

specified to restore the configuration files.

pg 58/59 then give some syntax for doing this from the command line.

Have a look and let me know if this answers the question.

oczkov · Answer

Now it's 100% clear.

I couldn't find this information using the popular seach engine. Seams like the powerlink content (I mean the public one) one is not well indexed, which is a space for improvement :-).

Eric - thank you very much for your professional help.

Regards,

S.

NetWorker

Networker, VADP and the RDMs in virtual mode

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