Den ons 13 maj 2020 kl 22:37 skrev Bryan Henderson <bryanh@xxxxxxxxxxxxxxxx >: > I'm surprised I couldn't find this explained anywhere (I did look), but ... > What is the pgmap and why does it get updated every few seconds on a tiny > cluster that's mostly idle? > > I was sure it was updated exactly once per second. > I do know what a placement group (PG) is and that when documentation talks > about placement group maps, it is talking about something else -- mapping > of > PGs to OSDs by CRUSH and OSD maps. > I thought it was a method (the method?) to know if a PG comes back from a crashed OSD/host, to know if it was up-to-date or old since it would have an older timestamp. Since using computer time and date is fraught with peril, having the whole cluster just bump that single number every second (and writing it to the PG on each write) would allow a mostly idle PG that comes back after an hour of unexpected downtime to easily know if it needs no recovery, a little bit of delta to get up-to-date or a full copy from the primary in order to become a part of the replica set for that PG. -- May the most significant bit of your life be positive. _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
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