So one more Veeam issue for you!
Had a problem where the backups to SAN where SLOW, I mean really slow….a 1TB server was taking 12 hours to complete and killing the servers performance!
So after talking with Veeam they checked out our logs and mentioned when we switched vCenters and reregistered our VM’s it seemed to have changed the ID (oldChangeId and curChangeId differed) meaning change block tracking or CBT was set to false (IsChangeTrackingAllowed: FALSE) and so tracking of what blocks had changed wouldn’t work and so meaning our backups crawled!!
To fix this we had to whats laid out here: http://www.veeam.com/KB1113
Which cleared up our issues.