we faced this error5 : Filesystem "dm-18": xfs_log_force: error 5 returned.

also we got this message:

Mount disappears & mounting it back gives errors.
10.50.2.71:/hostbackup
- - - - /hostbackup
[root@li root]# umount /hostbackup
[root@li root]#
[root@li root]#
[root@li root]# mount -a
mount: 10.50.2.71:/hostbackup failed, reason given by server: Not a directory

any idea about this issue