On Wed, Mar 14, 2018 at 5:48 AM, Lars Marowsky-Bree <lmb@xxxxxxxx> wrote: > On 2018-02-28T02:38:34, Patrick Donnelly <pdonnell@xxxxxxxxxx> wrote: > >> I think it will be necessary to reduce the actives to 1 (max_mds -> 1; >> deactivate other ranks), shutdown standbys, upgrade the single active, >> then upgrade/start the standbys. >> >> Unfortunately this didn't get flagged in upgrade testing. Thanks for >> the report Dan. > > This means that - when the single active is being updated - there's a > time when there's no MDS active, right? Yes. But the real outcome is not "no MDS [is] active" but "some or all metadata I/O will pause" -- and there is no avoiding that. During an MDS upgrade, a standby must take over the MDS being shutdown (and upgraded). During takeover, metadata I/O will briefly pause as the rank is unavailable. (Specifically, no other rank can obtains locks or communicate with the "failed" rank; so metadata I/O will necessarily pause until a standby takes over.) Single active vs. multiple active upgrade makes little difference in this outcome. > Is another approach theoretically feasible? Have the updated MDS only go > into the incompatible mode once there's a quorum of new ones available, > or something? I believe so, yes. That option wasn't explored for this patch because it was just disambiguating the compatibility flags and the full side-effects weren't realized. -- Patrick Donnelly _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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