Plesk is unable to save backup on CIFS (Samba) storage: Failed to close volume: (5) Input/output error

Symptoms

• Unable to run a full (large) backup at Plesk > Tools & Settings > Backup Manager. The process starts but fails with the errors like below:

  PLESK_ERROR: Unable to back up files from /var/www/vhosts/example.net owned by system user. Error: Failed to create archive: Failed to close volume: (5) Input/output error
  Warning: Subscription "example.com"
  Unable to back up files from /var/www/vhosts/example.com owned by system user. Error: Failed to create archive: Failed to close volume: (5) Input/output error
  Warning: Database "example_db"
  Unable to make database dump. Error: Failed to create archive: Failed to close volume: (5) Input/output error

• The /var/lib/psa/dumps directory is mounted on a CIFS-typed partition (in this example on 192.0.2.2 IP). Or DUMP_D variable points to this CIFS-storage (can be checked in /etc/psa/psa.conf).

• The following can be found in the output of dmesg:

  CONFIG_TEXT: [12345.6789] CIFS VFS: Server 192.0.2.2 has not responded in 120 seconds. Reconnecting...
  [98765.4321] CIFS VFS: Server 192.0.2.2 has not responded in 120 seconds. Reconnecting...

Cause

Bad connectivity between the Plesk and CIFS server.

Resolution

Contact with your network administrator and/or with administrator of CIFS server for further investigation.