Symptoms
An agent based vstor backup of a client running a version of DPX older than 4.5.2 may fail as follows:
10.0.85.226 5/21/2018 5:33:02 pm SNBSNP3069E 140271319746688: Position out of
boundary: start = 1087163629568, len = 18446743228137832448, device_size = 483183820800
10.0.85.226 5/21/2018 5:33:02 pm SNBSNP3069E 140271319746688: Failed to get list of
allocated blocks
In this case, the client was a Linux node but you may get the same error with a Windows based node.
Resolution
Upgrade the client to at least 4.5.2.