vDR and space requirement for snapshot?

[fgl]

Hello,

I know this question have been asked before as I've seen it on the forum in the past but for some reason the search function is not working for me so my apologise for asking it again.

If I have a VM with a 60GB vmdk does vDR require another 60GB of free space on the same datastore as the vmdk in order for vDR to make it's snapshot?

Thanks.

[jamesbowling]

In short, no.  Although snapshots can grow rapidly, especially if the particular VM is of high usage type.

[AndreTheGiant]

Usually snapshots take aroud the 10% of the virtual disk.

But, as written, it depends by the type of I/O.

If during the backup, start also a disk defrag inside the guest, then you can have the worste case (60 GB).

Andre

[fgl]

Hmm. Then I have a problem somewhere I'm not sure of.  I had to temporary move 2 VMs (1 Windows 2008 and 1 Windows 2003) from their normal location on a iSCSI SAN to the local storage on one of the ESXi 4.1 host and now I can't seem to back them up anymore.  I'm getting the dreaded 'failed to create snapshot for xxx, error -3960 (cannot quiesce virtual machine)' error.  I tried to do a manual snapshot without 'snapshot the virtual machines's memory' checked and it fails as well.  If I svmotion them back to the SAN storage then snapshots and vDR works but back to local storage snapshot fails.  Now the host only has 132GB of local storage with 23GB free after svmotioning the 2 VMs over so that is why I was wondering if it was a space issue.

[fgl]

Could the difference in block size and/or vmfs file system be the cause?  On the original SAN datastore the block size is 4MB and file system is VMFS 3.31 but on the local datastore the block size is 1MB and file system is VMFS 3.46.  The 2 VMs are running fine including after a reboot and reinstall of the vmtools, it's just that I can't do vDR or manual snapshots anymore when on the local datastore.

[AndreTheGiant]

Yes... block size is very important, and on VDR destination must be the greater block that you have.

See also: http://communities.vmware.com/docs/DOC-11920

Andre