From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1Jyagy-0005E2-7f for qemu-devel@nongnu.org; Tue, 20 May 2008 18:52:24 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1Jyagw-0005Dd-Oy for qemu-devel@nongnu.org; Tue, 20 May 2008 18:52:23 -0400 Received: from [199.232.76.173] (port=47363 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Jyagw-0005Da-KF for qemu-devel@nongnu.org; Tue, 20 May 2008 18:52:22 -0400 Received: from mail.codesourcery.com ([65.74.133.4]:55747) by monty-python.gnu.org with esmtps (TLS-1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1Jyagw-0003QU-0x for qemu-devel@nongnu.org; Tue, 20 May 2008 18:52:22 -0400 From: Paul Brook Subject: Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_DIRECT) Date: Tue, 20 May 2008 23:52:17 +0100 References: <1211283126.4314.70.camel@frecb07144> <48332AB9.3010707@codemonkey.ws> <20080520223602.GE27853@shareable.org> In-Reply-To: <20080520223602.GE27853@shareable.org> MIME-Version: 1.0 Content-Type: text/plain; charset="ansi_x3.4-1968" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200805202352.17807.paul@codesourcery.com> Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Blue Swirl , Laurent Vivier , Kevin Wolf > When sector-aligned guest offsets are converted to sector-unaligned > writes (e.g. due to qcow2 etc.), that property is no longer satisfied, > and power failure of the host disk can cause more damage than the > guest is designed to be resistant to. Seems like the easiest solution would be to have qcow always align its writes. We don't do on the fly compression, so it should be fairly easy to make this happen with minimal overhead. Paul