I am seeing very different backup speed when backing up VMs from the same SAN / drives. For example, Exchange is the fastest @ 70 MB/s (constant across multiple runs) and other VMs as low as 38. I am using the Microsoft iSCSI hardware provider to do off-host backup on a separate network. The Veeam server carries all the roles (proxy, repository and DB). I am backing up only 1 VM at a time, when my SAN / Network / Servers are almost idle. The bottleneck is reported to be the target by 76%, but looking at Performance Monitor, it is not really busy.
What can cause backup speed to vary that much?