From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefan Priebe - Profihost AG Subject: Re: recommanded cache setting for rbd image Date: Tue, 06 Nov 2012 08:34:15 +0100 Message-ID: <5098BD77.1050202@profihost.ag> References: <5097D2DD.2000006@profihost.ag> <50985257.3040304@inktank.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail.profihost.ag ([85.158.179.208]:39190 "EHLO mail.profihost.ag" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752495Ab2KFHeS (ORCPT ); Tue, 6 Nov 2012 02:34:18 -0500 In-Reply-To: <50985257.3040304@inktank.com> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Josh Durgin Cc: "ceph-devel@vger.kernel.org" Am 06.11.2012 00:57, schrieb Josh Durgin: > On 11/05/2012 06:53 AM, Stefan Priebe - Profihost AG wrote: >> Hello list, >> >> right now i'm testing rbd block devices with kvm using Default cache (no >> cache). >> >> Is there any recommanded value for RBD? (i don't wanna loose data) > > It acts like a well-behaved disk cache (i.e. it respects > flushes/barriers from the guest), so it's no more likely to cause data > loss than a local hard disk in the event of an unexpected shutdown. > > I recommend running it in writeback mode (the default when rbd cache = > true). The best cache size will depend on your workload and hardware. Thanks i'll check how this influence my disks and storage. Thanks! Stefan