From: Sage Weil <sage@inktank.com>
To: Stefan Priebe - Profihost AG <s.priebe@profihost.ag>
Cc: Mark Nelson <mark.nelson@inktank.com>,
Alexandre DERUMIER <aderumier@odiso.com>,
ceph-devel@vger.kernel.org
Subject: Re: Heavy speed difference between rbd and custom pool
Date: Tue, 19 Jun 2012 08:42:28 -0700 (PDT) [thread overview]
Message-ID: <Pine.LNX.4.64.1206190840550.21853@cobra.newdream.net> (raw)
In-Reply-To: <4FE07B2A.7080209@profihost.ag>
On Tue, 19 Jun 2012, Stefan Priebe - Profihost AG wrote:
> Am 19.06.2012 15:01, schrieb Mark Nelson:
> > On 06/19/2012 01:32 AM, Stefan Priebe - Profihost AG wrote:
> > > Am 19.06.2012 06:41, schrieb Alexandre DERUMIER:
> > > > Hi Stephann
> > > > recommandations are 30-50 PGS by osd if I remember.
> > > >
> > > rbd, data and metadata have 2176 PGs with 12 OSD. This is 181,333333333
> > > per OSD?!
> > >
> > > Stefan
> >
> > That's probably fine, it just means that you will have a better
> > pseudo-random distribution of OSD combinations (It does have higher
> > cpu/memory overhead though). Figuring out how many PGs you should have
> > per OSD depends on a lot of factors including how many OSDs you have,
> > how many nodes, CPU, memory, etc. I'm guessing ~180 per OSD won't cause
> > problems. On the other hand, with low OSD counts you could probably have
> > fewer and be fine too.
>
> But this number 2176 of PGs were set while doing mkcephfs - how is it
> calculated?
num_pgs = num_osds << osd_pg_bits
which is configurable via --osd-pg-bits N or ceph.conf (at mkcephfs time).
The default is 6.
sage
next prev parent reply other threads:[~2012-06-19 15:42 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-18 21:39 Heavy speed difference between rbd and custom pool Stefan Priebe
2012-06-18 22:23 ` Mark Nelson
2012-06-18 22:41 ` Dan Mick
2012-06-19 6:06 ` Stefan Priebe
2012-06-19 6:30 ` Stefan Priebe - Profihost AG
2012-06-19 4:41 ` Alexandre DERUMIER
2012-06-19 6:32 ` Stefan Priebe - Profihost AG
2012-06-19 13:01 ` Mark Nelson
2012-06-19 13:14 ` Stefan Priebe - Profihost AG
2012-06-19 14:05 ` bad performance fio random write - rados bench random write to compare? Alexandre DERUMIER
2012-07-02 19:52 ` Gregory Farnum
2012-07-03 7:31 ` Stefan Priebe - Profihost AG
2012-06-19 15:42 ` Sage Weil [this message]
2012-06-19 16:24 ` Heavy speed difference between rbd and custom pool Stefan Priebe
2012-06-19 16:27 ` Sage Weil
2012-06-19 16:29 ` Dan Mick
2012-06-20 6:46 ` Stefan Priebe - Profihost AG
2012-06-20 23:21 ` Dan Mick
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