On Fri, Jul 29, 2016 at 01:48:43PM +0200, Wido den Hollander wrote: > > > Op 29 juli 2016 om 13:20 schreef Chengwei Yang <chengwei.yang.cn@xxxxxxxxx>: > > > > > > Hi Christian, > > > > Thanks for your reply, and since I do really don't like the HEALTH_WARN and it > > not allowed to decrease pg_num of a pool. > > > > So can I just remove the default **rbd** pool and re-create it by using `ceph osd > > pool create`? > > > > Yes, you can. > > > If so, is there anything I have to pay attention to? > > > > Your data! Are you sure there is no data in the pool? If so, make sure you back that up first. Otherwise you can remove the pool and re-create it. The pool is not required, so if you don't use it you can also just remove it. Wow! great to know that, thanks Wido, much appreciate! -- Thanks, Chengwei > > Wido > > > Thanks in advance! > > > > On Fri, Jul 29, 2016 at 11:47:59AM +0900, Christian Balzer wrote: > > > On Fri, 29 Jul 2016 09:59:38 +0800 Chengwei Yang wrote: > > > > > > > Hi list, > > > > > > > > I just followed the placement group guide to set pg_num for the rbd pool. > > > > > > > How many other pools do you have, or is that the only pool? > > > > > > The numbers mentioned are for all pools, not per pool, something that > > > isn't abundantly clear from the documentation either. > > > > > > > " > > > > Less than 5 OSDs set pg_num to 128 > > > > Between 5 and 10 OSDs set pg_num to 512 > > > > Between 10 and 50 OSDs set pg_num to 4096 > > > > If you have more than 50 OSDs, you need to understand the tradeoffs and how to > > > > calculate the pg_num value by yourself > > > > For calculating pg_num value by yourself please take help of pgcalc tool > > > > " > > > > > > > You should have headed the hint about pgcalc, which is by far the best > > > thing to do. > > > The above numbers are an (imprecise) attempt to give a quick answer to a > > > complex question. > > > > > > > Since I have 40 OSDs, so I set pg_num to 4096 according to the above > > > > recommendation. > > > > > > > > However, after configured pg_num and pgp_num both to 4096, I found that my > > > > ceph cluster in **HEALTH_WARN** status, which does surprised me and still > > > > confusing me. > > > > > > > PGcalc would recommend 2048 PGs at most (for a single pool) with 40 OSDs. > > > > > > I assume the above high number of 4096 stems from the wisdom that with > > > small clusters more PGs than normally recommended (100 per OSD) can be > > > helpful. > > > It was also probably written before those WARN calculations were added to > > > Ceph. > > > > > > The above would better read: > > > --- > > > Use PGcalc! > > > [...] > > > Between 10 and 20 OSDs set pg_num to 1024 > > > Between 20 and 40 OSDs set pg_num to 2048 > > > > > > Over 40 definitely use and understand PGcalc. > > > --- > > > > > > > > cluster bf6fa9e4-56db-481e-8585-29f0c8317773 > > > > health HEALTH_WARN > > > > too many PGs per OSD (307 > max 300) > > > > > > > > I see the cluster also says "4096 active+clean" so it's safe, but I do not like > > > > the HEALTH_WARN in anyway. > > > > > > > You can ignore it, but yes, it is annoying. > > > > > > > As I know(from ceph -s output), the recommended pg_num per OSD is [30, 300], any > > > > other pg_num out of this range with bring cluster to HEALTH_WARN. > > > > > > > > So what I would like to say: is the document misleading? Should we fix it? > > > > > > > Definitely. > > > > > > Christian > > > -- > > > Christian Balzer Network/Systems Engineer > > > chibi@xxxxxxx Global OnLine Japan/Rakuten Communications > > > http://www.gol.com/ > > > > -- > > Thanks, > > Chengwei > > _______________________________________________ > > ceph-users mailing list > > ceph-users@xxxxxxxxxxxxxx > > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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