From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1KLIZU-0000z3-6L for qemu-devel@nongnu.org; Tue, 22 Jul 2008 10:10:32 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1KLIZS-0000yK-JK for qemu-devel@nongnu.org; Tue, 22 Jul 2008 10:10:31 -0400 Received: from [199.232.76.173] (port=54254 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1KLIZS-0000yF-9v for qemu-devel@nongnu.org; Tue, 22 Jul 2008 10:10:30 -0400 Received: from mail2.shareable.org ([80.68.89.115]:38272) by monty-python.gnu.org with esmtps (TLS-1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1KLIZR-00064x-OK for qemu-devel@nongnu.org; Tue, 22 Jul 2008 10:10:30 -0400 Received: from jamie by mail2.shareable.org with local (Exim 4.63) (envelope-from ) id 1KLIux-0005Xi-4i for qemu-devel@nongnu.org; Tue, 22 Jul 2008 15:32:43 +0100 Date: Tue, 22 Jul 2008 15:32:43 +0100 From: Jamie Lokier Subject: Re: [Qemu-devel] qcow2 - safe on kill? safe on power fail? Message-ID: <20080722143242.GC20829@shareable.org> References: <47CF0E0C.9030807@quinthar.com> <47CF16C5.6040102@codemonkey.ws> <20080721181031.GA31773@shareable.org> <4884E6F1.5020205@codemonkey.ws> <20080721212604.GA2823@shareable.org> <48850A5A.3070106@codemonkey.ws> <488578CA.4000402@qumranet.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <488578CA.4000402@qumranet.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 Avi Kivity wrote: > The exposure window with qemu is not small. It's as large as the page > cache of the host. Ouch, that's a good point. I hadn't thought of that. With cache=off, the exposure window is as large as the I/O scheduling and disk seek time between the multiple blocks written during sector allocation. Given how often sector allocation occurs, it's not small. I think I'm going to just stop using QCOW2, bite the bullet, and use large disks and flat images for all production VMs. The small but looking-plausible possibility of losing a whole valuable machine due to niggling things like a rare QEMU crash or host crash is very uncool. -- Jamie