Experienced on Symantec NetBackup 7 on Server 2008 R2 restoring VMs on vSphere 4.1
Discussed and solved here: Symantec Support forum post
Backing up VMs go smooth although testing out restoring a vm (to its original location) after I delete it from disk through vSphere. I kicked off the restore, vSphere did create the VM and it created a snapshot. Then within the View Status of NetBackup restore constantly started repeating “Virtual machine restore: file write failed” and virtual center constantly repeats “Allocate blocks” in its recent tasks window and it shows it completing.
Apparently there is a bug with NetBackup 7 and restoring VMware vmdks with “Try all types”. The types that are provided are SAN, NBD, and SAN then NBD. The issue is with restoring with the SAN option which is NetBackups first decision. Once I changed it to NBD, the restore was successful within about an hour of starting it.