>>We haven't really quantified that yet. In particular, it's going to >>depend on how many objects are accessed within a period; the OSD sizes >>them based on the previous access count and the false positive >>probability that you give it
Ok, thanks Greg. Another question, the doc describe how the objects are going from cache tier to base tier. But how does it work from base tier to cache tier ? (cache-mode writeback) Does any read on base tier promote the object in the cache tier ? Or they are also statistics on the base tier ? (I tell the question, because I have cold datas, but I have full backups jobs running each week, reading all theses cold datas) ----- Mail original ----- De: "Gregory Farnum" <g...@inktank.com> À: "Alexandre DERUMIER" <aderum...@odiso.com> Cc: "ceph-users" <ceph-users@lists.ceph.com> Envoyé: Mercredi 11 Juin 2014 21:56:29 Objet: Re: [ceph-users] tiering : hit_set_count && hit_set_period memory usage ? On Wed, Jun 11, 2014 at 12:44 PM, Alexandre DERUMIER <aderum...@odiso.com> wrote: > Hi, > > I'm reading tiering doc here > http://ceph.com/docs/firefly/dev/cache-pool/ > > " > The hit_set_count and hit_set_period define how much time each HitSet should > cover, and how many such HitSets to store. Binning accesses over time allows > Ceph to independently determine whether an object was accessed at least once > and whether it was accessed more than once over some time period (“age” vs > “temperature”). Note that the longer the period and the higher the count the > more RAM will be consumed by the ceph-osd process. In particular, when the > agent is active to flush or evict cache objects, all hit_set_count HitSets > are loaded into RAM" > > about how much memory do we talk here ? any formula ? (nr object x ? ) We haven't really quantified that yet. In particular, it's going to depend on how many objects are accessed within a period; the OSD sizes them based on the previous access count and the false positive probability that you give it. -Greg Software Engineer #42 @ http://inktank.com | http://ceph.com _______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
