From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wido den Hollander Subject: Re: Recommended number of pools, one Q. ever wanted to ask Date: Tue, 28 Feb 2012 16:51:11 +0100 Message-ID: <4F4CF7EF.7010505@widodh.nl> References: <4F4C9FE9.7000808@filoo.de> <4F4CA17F.4070007@widodh.nl> <4F4CA380.2010004@filoo.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from smtp02.mail.pcextreme.nl ([109.72.87.138]:42884 "EHLO smtp02.mail.pcextreme.nl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965614Ab2B1PvN (ORCPT ); Tue, 28 Feb 2012 10:51:13 -0500 In-Reply-To: <4F4CA380.2010004@filoo.de> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Oliver Francke Cc: ceph-devel@vger.kernel.org Hi, On 02/28/2012 10:50 AM, Oliver Francke wrote: > Well, > > On 02/28/2012 10:42 AM, Wido den Hollander wrote: >> Hi, >> >> On 02/28/2012 10:35 AM, Oliver Francke wrote: >>> Hi *, >>> >>> well, there was once a comment on our layout in means of "too many >>> pools". >>> Our setup is to have a pool per customer, to simplify the view on used >>> storage >>> capacity. >>> So, if we have - in a couple of months, we hope - more then some hundred >>> customers, this setup was not recommended, cause the whole system is not >>> designed for handling that. ( Sage) >>> >>> What does "not recommended" mean? Is it, that per OSD the used memory >>> will be >>> too high? >> >> Yes. Every new pool you create will consume some memory on the OSD. So >> if you start creating a lot of pools, you will also start consuming >> more and more memory. >> >> I haven't followed this lately, but that is the current information I >> have. >> >> The number of objects in a pool is also not a problem, you can have >> millions without any issues. It's the number of pools which will haunt >> you later on. > > thnx for the quick reply, so if we can imagine, that the number of pool > per OSD is > the limiting factor, we shall not have more than let's say ~100, means, > we shall be > safe. IIRC the number of pools is a problem, but for every pool you have a number of Placement Groups (PG's) (pg_num). Each PG eats a small amount of memory. As the number of OSD's increases you also want to increase the number of PG's, this improves performance. But as you have more PG's per pool, you start increasing memory usage. Now, PG's will be spread out over your OSD's, but it could still increase the usage. This probably won't be a problem with 500 pools, or maybe a thousand pools (but it could), but going above that could be a problem. Wido > >> >> Wido > > best regards, > > Oliver. > >> >>> Is this a general performance issue? >>> >>> Well, if we read "pool", this gave us the basic idea/concept to put all >>> per-customers >>> data into it. >>> >>> Please sched some light in 8-) >>> >>> Kind regards, >>> >>> Oliver. >>> >> > >