Any user access to an object promotes it into the cache pool. On Wednesday, June 11, 2014, Alexandre DERUMIER <aderum...@odiso.com> wrote:
> >>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 <javascript:;>> > À: "Alexandre DERUMIER" <aderum...@odiso.com <javascript:;>> > Cc: "ceph-users" <ceph-users@lists.ceph.com <javascript:;>> > 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 <javascript:;>> 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 > -- Software Engineer #42 @ http://inktank.com | http://ceph.com
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