On Sat, May 26, 2018 at 11:51 AM Bryan Henderson <[email protected]> wrote:
> >> Suppose I lost all monitors in a ceph cluster in my laboratory. I have > >> all OSDs intact. Is it possible to recover something from Ceph? > > > >Yes, there is. Using ceph-objectstore-tool you are able to rebuild the > >MON database. > > > >BUT, this isn't something you would really want to do as you loose your > >cephx keys and such and getting them all back will be a total nightmare. > > According to the section of the manual on this, TROUBLESHOOTING MONITORS -> > RECOVERY USING OSDS, another thing that you lose when you use > ceph-objectstore-tool --op update-mon-db to recover a lost monitor > database is > the MDS maps. > > That seems like a pretty casual way of saying if your monitor database gets > corrupted, you can kiss your entire cephfs filesystem goodbye. Is that > what > it means? Luckily; it's not. I don't remember if the MDS maps contain entirely ephemeral data, but on the scale of cephfs recovery scenarios that's just about the easiest one. Somebody would have to walk through it; you probably need to look up the table states and mds counts from the RADOS store and generate a new (epoch 1 or 2) mdsmap which contains those settings ready to go. Or maybe you just need to "create" a new cephfs on the prior pools and set it up with the correct number of MDSes. At the moment the mostly-documented recovery procedure probably involves recovering the journals, flushing everything out, and resetting the server state to a single MDS, and if you lose all your monitors there's a good chance you need to be going through recovery anyway, so...*shrug* -Greg > Is there a way to recover the MDS maps or otherwise gain access to > all the files once you've recovered access to the OSDs? > > -- > Bryan Henderson San Jose, California > _______________________________________________ > ceph-users mailing list > [email protected] > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >
_______________________________________________ ceph-users mailing list [email protected] http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
