From mboxrd@z Thu Jan 1 00:00:00 1970 From: Josh Durgin Subject: Re: recommanded cache setting for rbd image Date: Mon, 05 Nov 2012 15:57:11 -0800 Message-ID: <50985257.3040304@inktank.com> References: <5097D2DD.2000006@profihost.ag> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-da0-f46.google.com ([209.85.210.46]:60763 "EHLO mail-da0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752566Ab2KEX5a (ORCPT ); Mon, 5 Nov 2012 18:57:30 -0500 Received: by mail-da0-f46.google.com with SMTP id n41so2905751dak.19 for ; Mon, 05 Nov 2012 15:57:30 -0800 (PST) In-Reply-To: <5097D2DD.2000006@profihost.ag> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Stefan Priebe - Profihost AG Cc: "ceph-devel@vger.kernel.org" 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.