I am using Backup Exec 2010 R3 to backup my VMs using it's VMware agent and using SAN transport as opposed to network level backups. I've noticed that some of my VMs backed up nice and fast. Nearly 4 GB/minute, while others limp along at 1GB/minute or less.
I was able to find a VM that backed up fast and one that was slow which used the same RAID groups on my SAN and about the nearly the same datastore. After I migrated the disk of the slower server to the datastore where the backups ran fast for the other server, I noticed backup speeds similar to the fast server in this comarison. So, then I moved the disk back to the origional location and it still backs up fast now.
On both servers their disks are thin disks, and are roughly the same size. I'm really just trying to figure out what happened here. Did I do some sort of defrag by migrating a thin disk to another datastore? Do thin disks fragment and degrade over time within the VMFS due to the nature of how they expand?
If anyone knows of a good explaination or has experienced this themselves, I'm all ears. In the mean time, I'm going to try this on a few other slow to backup servers and see if I can get the same result!
-Thanks