From mboxrd@z Thu Jan 1 00:00:00 1970 From: Josh Durgin Subject: Re: how to debug slow rbd block device Date: Wed, 23 May 2012 12:54:52 -0700 Message-ID: <4FBD408C.5000504@inktank.com> References: <4FBB8A5B.9010500@profihost.ag> <4FBBEBC8.1000205@profihost.ag> <1C70F3FB753C4AEC97247E04FAE3C733@inktank.com> <4FBBF74C.9020608@profihost.ag> <45F1742481D84E7A90951816DB23609F@inktank.com> <4FBBFE7B.4060406@profihost.ag> <65E9589544C4489F93761035433ADC01@inktank.com> <4FBC811F.5060004@profihost.ag> <4FBC83F3.7070400@inktank.com> <4FBC8B41.1020300@profihost.ag> <4FBC8F8F.6060004@inktank.com> <4FBC904A.7090407@profihost.ag> <4FBC92E2.5020807@inktank.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mail-pb0-f46.google.com ([209.85.160.46]:43173 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753061Ab2EWTyz (ORCPT ); Wed, 23 May 2012 15:54:55 -0400 Received: by pbbrp8 with SMTP id rp8so10336408pbb.19 for ; Wed, 23 May 2012 12:54:55 -0700 (PDT) In-Reply-To: Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Andrey Korolyov Cc: ceph-devel On 05/23/2012 02:03 AM, Andrey Korolyov wrote: > Hi Josh, > > Can you please answer to list on this question? It is important when > someone wants to build HA KVM cluster on the rbd backend and needs to > wc cache. Thanks! > > On Wed, May 23, 2012 at 10:30 AM, Josh Durgin wrote: >> On 05/22/2012 11:18 PM, Stefan Priebe - Profihost AG wrote: >>> >>> Hi, >>> >>>>> So try enabling RBD writeback caching =E2=80=94 see http://marc.i= nfo >>>>> /?l=3Dceph-devel&m=3D133758599712768&w=3D2 >>>>> will test tomorrow. Thanks. >>> >>> Can we path this to the qemu-drive option? >> >> >> Yup, see http://article.gmane.org/gmane.comp.file-systems.ceph.devel= /6400 >> >> The normal qemu cache=3Dwriteback/writethrough/none option will work= in qemu >> 1.2. >> >> Josh > > By the way, is it possible to flush cache outside? I may need that fo= r > VM live migration and such hook will be helpful. Qemu will do that for you in many cases, but it looks like we need to=20 implement bdrv_invalidate_cache to make live migration work. http://tracker.newdream.net/issues/2467 librbd itself flushes the cache when a snapshot is created or the image= =20 is closed, but there's no way to trigger it directly right now. http://tracker.newdream.net/issues/2468 -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html