Hi Loic, > By restoring the fsid file from the back, presumably. I did not think of that when you showed the ceph-osd mkfs line, but it makes sense. This is not the ceph fsid. Yeah, I though about that and I saw fsid and ceph_fsid, but I wasn't just that just replacing the file would be enough or if the fsid was used somewhere else and this could yield some weird state ... > root at bm0015:/var/lib/ceph/osd/ceph-1# grep fsid /etc/ceph/ceph.conf > fsid = 571bb920-6d85-44d7-9eca-1bc114d1cd75 Weird, I don't have a fsid in my ceph.conf ... Cheers, Sylvain