Backup to NFS repository may hang

After the backup job starts, some task may hang if all of the following conditions are met:

• The backup repository type is the NFS repository.
• A Linux server is selected as a gateway server explicitly or it was selected by the automatic selection from options.
• NFS v3 is used to access the NFS repository.

In this case, the target agent log shows the "There was no finalized server sessions during the last 60 minutes." message, for example:

[29.10.2019 14:03:20.405] <140689077683968> stg| Opening storage [/mnt/Veeam/{d19c5d30-90a5-4d77-a9a0-3f59727a49c6}/<Job name>/<Backup file name>.vib] for read/write access.
[29.10.2019 14:03:20.406] <140689077683968> stg|   Opening storage file [HostFS:///mnt/Veeam/{d19c5d30-90a5-4d77-a9a0-3f59727a49c6}/<Job name>/<Backup file name>.vib.vib].
[29.10.2019 14:03:20.406] <140689077683968> stg|     Applying exclusive lock on file [/mnt/Veeam/{d19c5d30-90a5-4d77-a9a0-3f59727a49c6}/<Job name>/<Backup file name>.vib.vib].
[29.10.2019 14:23:20.405] <140689069291264> cli| WARN|MTA invoke thread : timed out for backup events. Wait cycle will be resumed for '336' hours.
[29.10.2019 15:03:07.707] <140689469306624> srv|   There was no finalized server sessions during the last 60 minutes.
[29.10.2019 16:03:07.715] <140689469306624> srv|   There was no finalized server sessions during the last 60 minutes.

Access to nlockmanager is not configured on the NFS server.

Make sure that all required ports are configured properly:
 

TCP and UDP port 2049 for NFS.
TCP and UDP port 111 (rpcbind/sunrpc).
TCP and UDP port specified with MOUNTD_PORT
TCP and UDP port specified with STATD_PORT
TCP port specified with LOCKD_TCPPORT
UDP port specified with LOCKD_UDPPORT