From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1L6xqY-0005hQ-48 for qemu-devel@nongnu.org; Sun, 30 Nov 2008 20:45:10 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1L6xqV-0005ci-6r for qemu-devel@nongnu.org; Sun, 30 Nov 2008 20:45:09 -0500 Received: from [199.232.76.173] (port=34553 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1L6xqU-0005cJ-VD for qemu-devel@nongnu.org; Sun, 30 Nov 2008 20:45:07 -0500 Received: from main.gmane.org ([80.91.229.2]:51518 helo=ciao.gmane.org) by monty-python.gnu.org with esmtps (TLS-1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1L6xqU-0000RB-J3 for qemu-devel@nongnu.org; Sun, 30 Nov 2008 20:45:06 -0500 Received: from root by ciao.gmane.org with local (Exim 4.43) id 1L6xqQ-0000Te-7f for qemu-devel@nongnu.org; Mon, 01 Dec 2008 01:45:02 +0000 Received: from adsl-69-234-198-192.dsl.irvnca.pacbell.net ([69.234.198.192]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 01 Dec 2008 01:45:02 +0000 Received: from w41ter by adsl-69-234-198-192.dsl.irvnca.pacbell.net with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 01 Dec 2008 01:45:02 +0000 From: walt Date: Sun, 30 Nov 2008 17:40:34 -0800 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: news Subject: [Qemu-devel] qemu-img commit -- is there a limit on file sizes? 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 Some background for my question: I've been trying to install and then update Windows Vista using kvm. Everything works great until I use 'qemu-img commit' to apply all the Windows Updates to my original base install of Vista. After doing the qemu-img commit step, the backing file is now corrupt, 100% reproducibly. I don't have the same problem with Windows XP, however, and I wondered if the problem is caused by the sheer size of the commit that Vista requires. When I install XP, then windows-update, and then qemu-img commit the updates, I'm committing about 1GB of updates to a 3GB backing file. When I install Vista and then later commit the Vista updates, I'm committing a 3GB file to a 6GB backing file, and that's when the corruption happens every time. So I tried an experiment with Vista -- I deliberately limit the number of windows updates I allow at any one time, and then use qemu-img commit after each small update. Voila, everything now works perfectly -- no file corruption! And that's why I suspect there is a functional limit to the size of each commit I can do with qemu-img. Any thoughts or possible diagnostic maneuvers to be tried? Thanks! (BTW, I get the same results using 32-bit linux and 64-bit linux on the same amd64 machine, using both gcc3 and gcc4.)