System state backup fails with Child Process died unexpectedly (81261)

Backup is system state backups that take VSS snapshots when backing up the registry can fail with errors similar to

Background 2010/11/13 21:16:36 0 System NVSERVER Machine 'NVCLIENT' has gone down
Error 2010/11/13 21:16:36 620 Jobs NVSERVER Child Process died unexpectedly
Error 2010/11/13 21:16:36 620 Jobs NVSERVER Fatal error: Backup Died Unexpectedly
Error 2010/11/13 21:16:36 620 Jobs NVSERVER Job Status: Backup Failed

The problem may also appear as:

Job Message 2010/11/13 21:16:36 620 Data Plugin NVCLIENT Backing up the registry
Error 2010/11/13 21:16:36 620 Jobs NVSERVER Job manager lost message channel unexpectedly

Monitoring CPU usage during backup showed DFS replication using high amounts of CPU. Logging of DFS replication was set on level 4

DFS replication is part of VSS, so when we create the volume show copy during the system state backup with logging set to 4 (verbose) the CPU usage goes so high that at times netvault does not receive a response to its UDP broadcast and a network timeout between the client and server cause the backup to fail.

Change the DFS replication logging level from 4 to 1 by referring to http://support.microsoft.com/kb/958893

Note: similar problems could be caused by any process taking to much CPU time so we need to look to see which process is consuming the CPU time during the backup.

Explanation:
The DFS replication logging on the client consumed high amount of CPU which caused a network timeout between the netvault client and netvault server because the client was to busy to respond to the UDP broadcast with expected time.