looking at binary log we see Backup failed because the NetVault server lost communication with the client 'clientX' as we can see reported in the binary log extract below.
Background 2015/08/09 20:31:56 N/A System NVserver NetVault Backup running on 'clientX' has not responded to messages
Error 2015/08/09 20:31:56 14396 Jobs NVserver Process running on 'clientx' has exited unexpectedly
Network communication problem
1/ modify the following values on the NetVault server and the client
Network settings to improve network connections.
Note NetVault restart is required to apply the below configuration changes.
Go to the “Network Manager” tab within the Configurator and change “Time in seconds to complete a remote connection” from 30 to 60.
Then change "Time wait before dropping inactive connection" from 300 to 600.
Also change “Keep Alive Rate” from 15 to 7.
And the last two:
“Time between availability broadcasts” from 300 to 600.
“Time between security broadcasts” from 300 to 600.
2/ if the client has more than 1 IPaddress we should setup preferred addressing, barring the addresses that are not used by NetVault and designating the address we want NetVault to use.
See KB below on how to do this:
https://support.quest.com/netvault-backup/kb/78927
3/ is firewall enabled on the client, if so have you configured the required firewall rules for NetVault.
To check the if the firewall is causing the backup failures as a test disabling the firewall and running the backup will prove if the firewall is cause of the problem.
On NetVault 10 we can check firewall with firewall test in manage client.
To set the windows firewall rules see URL’s below for NetVault 9.2 and below and NetVault 10:
NetVault 10: https://support.quest.com/netvault-backup/kb/146029
NetVault 9.2 and below: https://support.quest.com/netvault-backup/kb/79286
4/ perform the following tests, to make sure that NVBU can communicate freely amongst NetVault Server, all Clients and backup devices, otherwise causes backup/media/device/communication issues:
