> Of course -- the mons can't tell the difference! That is really unfortunate, it would be nice to know if the filesystem has been degraded and to what degree.
> You must have standbys for high availability. This is the docs. Ok but what if you have your standby go down and a master go down. This could happen in the real world and is a valid error scenario. Also there is a period between when the standby becomes active what happens in-between that time? > It depends(tm) on how the metadata is distributed and what locks are held by each MDS. Your saying depending on which mds had a lock on a resource it will block that particular POSIX operation? Can you clarify a little bit? > Standbys are not optional in any production cluster. Of course in production I would hope people have standbys but in theory there is no enforcement in Ceph for this other than a warning. So when you say not optional that is not exactly true it will still run. On Thu, Apr 26, 2018 at 3:37 PM Patrick Donnelly <[email protected]> wrote: > On Thu, Apr 26, 2018 at 3:16 PM, Scottix <[email protected]> wrote: > > Updated to 12.2.5 > > > > We are starting to test multi_mds cephfs and we are going through some > > failure scenarios in our test cluster. > > > > We are simulating a power failure to one machine and we are getting mixed > > results of what happens to the file system. > > > > This is the status of the mds once we simulate the power loss considering > > there are no more standbys. > > > > mds: cephfs-2/2/2 up > > {0=CephDeploy100=up:active,1=TigoMDS100=up:active(laggy or crashed)} > > > > 1. It is a little unclear if it is laggy or really is down, using this > line > > alone. > > Of course -- the mons can't tell the difference! > > > 2. The first time we lost total access to ceph folder and just blocked > i/o > > You must have standbys for high availability. This is the docs. > > > 3. One time we were still able to access ceph folder and everything > seems to > > be running. > > It depends(tm) on how the metadata is distributed and what locks are > held by each MDS. > > Standbys are not optional in any production cluster. > > -- > Patrick Donnelly >
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