Why the Gluster volume is unreachable and the 'gluster volume status' shows offline ?

Issue

• Why the Gluster volume is unreachable and the 'gluster volume status' shows offline ?

• Gluster volume become unreachable from 2 nodes at the same time without clear reason why this happened.

~Snippet from terminal,

[root@node1 ~]# gluster volume status test-vol
Gluster process                                                       TCP Port         RDMA Port      Online  Pid
------------------------------------------------------------------------------
Brick x.x.x.x:/bricks/brick_test1                                   N/A            N/A              N     22022
Brick x.x.x.x:/bricks/brick_test2                                   N/A            N/A              N     19784