From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefan Priebe Subject: Re: how to debug slow rbd block device Date: Tue, 22 May 2012 23:00:43 +0200 Message-ID: <4FBBFE7B.4060406@profihost.ag> References: <4FBB8A5B.9010500@profihost.ag> <4FBBEBC8.1000205@profihost.ag> <1C70F3FB753C4AEC97247E04FAE3C733@inktank.com> <4FBBF74C.9020608@profihost.ag> <45F1742481D84E7A90951816DB23609F@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.profihost.ag ([85.158.179.208]:48772 "EHLO mail.profihost.ag" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753350Ab2EVVAp (ORCPT ); Tue, 22 May 2012 17:00:45 -0400 In-Reply-To: <45F1742481D84E7A90951816DB23609F@inktank.com> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Greg Farnum Cc: ceph-devel@vger.kernel.org Am 22.05.2012 22:49, schrieb Greg Farnum: > Anyway, it looks like you're just paying a synchronous write penalty What does that exactly mean? Shouldn't one threaded write to four=20 260MB/s devices gives at least 100Mb/s? > since with 1 write at a time you're getting 30-40MB/s out of rados be= nch, but with 16 you're getting>100MB/s. >(If you bump up past 16 or increase the size of each with -b you may=20 find yourself getting even more.) yep noticed that. > So try enabling RBD writeback caching =E2=80=94 see http://marc.info/= ?l=3Dceph-devel&m=3D133758599712768&w=3D2 will test tomorrow. Thanks. Stefan -- 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