Veeam backups may fail after Storage vMotion to VMFS 3 volume

We recently had an issue whereby after performing a Storage vMotion from one VMFS 3 volume to another, certain Veeam backup jobs (our larger servers) were failing. We’re running VMware ESXi 4.1 U1 and vCenter 4.1.

Upon investigation it transpired that the new (target) VMFS volume was formatted with a 1MB block size, and the original (source) VMFS volume has 4MB blocks. This had the upshot of preventing the Veeam server from being able to create large VMware snapshots on the new volume due to the file size constraints of a VMFS 3 volume with 1MB blocks, whereas on a 4MB block size VMFS 3 volume this was possible.

The workaround for this was to perform a Storage vMotion to migrate the Veeam server’s files back to a VMFS data store formatted with a 4MB (or larger) block size.

The resolution for this would be to upgrade to vSphere 5 and upgrade the VMFS volumes to VMFS 5, which supports larger file sizes with a 1MB block size.


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