As suspected there are directories (gvol0, gvol1) inside the volume with root- gfid. Can you please check and confirm if these paths ("/gluster/brick1/gvol1" and "/gluster/brick1/gvol0") were used as bricks for any volume earlier at any point of time.
Have posted below two fixes upstream for review - http://review.gluster.org/#/c/14278 https://review.gerrithub.io/275930
any response from customer?
No, the customer has basically reached the end of the evaluation period and is in the process of extending it through sales.