From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wido den Hollander Subject: Re: What the ceph do when detecting one OSD overloaded? Date: Fri, 06 Jun 2014 12:35:12 +0200 Message-ID: <53919960.3010903@42on.com> References: <53917B8A.4000204@42on.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from websrv.42on.com ([31.25.102.167]:60074 "EHLO websrv.42on.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750803AbaFFKfQ (ORCPT ); Fri, 6 Jun 2014 06:35:16 -0400 In-Reply-To: Sender: ceph-devel-owner@vger.kernel.org List-ID: To: zou wonder Cc: ceph-devel@vger.kernel.org On 06/06/2014 11:27 AM, zou wonder wrote: > Hi Wido: > > Thanks for your kindness, i checked the codes just now, seems there > were no overload related thing in CRUSH codes. It is a little bit not > consistent with the CRUSH paper. > So if the %100 utilized OSD is returned, the objects will still be > written on the underlined storage device? > Yes. If the OSD is up/in it will be selected by CRUSH and data will be read from it and written to it. Again, having one OSD being 100% utilized and the rest 40% is not something you'll see very often since you stripe data over objects. > How about the device failure case? All the objects on the failure > device will be replicated to the good ones? once the device is > recoverd, the data will be replicated back? When the OSD fails recovery will kick in after 5 minutes and the data will find a new location. If the OSD comes back, the data goes back to that OSD. > > Best Regards > Zou > > On Fri, Jun 6, 2014 at 4:27 PM, Wido den Hollander wrote: >> On 06/06/2014 10:14 AM, zou wonder wrote: >>> >>> Hi buddies, >>> >>> I am doing investigation on Ceph and Swift,and I am newbie to Ceph. >>> >>> I am unclear to the behaviour of the Ceph when there is overload >>> situation. >>> According to the doc, when Ceph do CRUSH, if it find the OSD is overload, >>> it will skip it to select the other OSD. It means if the OSD don't get >>> overloaded >>> the object should be put in this OSD. So how about the original on put on >>> this OSD when it is not get overloaded? >>> Can we read it ? When doing CRUSH , the OSD will be skip. >>> >> >> CRUSH will not take any performance characteristics into account. If a OSD >> is 100% utilized it will still be selected by CRUSH. >> >> Keep in mind however that Block Devices are striped in 4MB chunks and the >> same happens for Objects stored via the RADOS Gateway. >> >>> If my understanding is wrong, please correct me. >>> >>> Best Regards, >>> zou >>> -- >>> To unsubscribe from this list: send the line "unsubscribe ceph-devel" in >>> the body of a message to majordomo@vger.kernel.org >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>> >> >> >> -- >> Wido den Hollander >> 42on B.V. >> Ceph trainer and consultant >> >> Phone: +31 (0)20 700 9902 >> Skype: contact42on -- Wido den Hollander 42on B.V. Ceph trainer and consultant Phone: +31 (0)20 700 9902 Skype: contact42on