From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1G7J7z-0005sL-S7 for qemu-devel@nongnu.org; Sun, 30 Jul 2006 17:47:15 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1G7J7y-0005rl-Dq for qemu-devel@nongnu.org; Sun, 30 Jul 2006 17:47:15 -0400 Received: from [199.232.76.173] (helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1G7J7y-0005re-5q for qemu-devel@nongnu.org; Sun, 30 Jul 2006 17:47:14 -0400 Received: from [81.29.64.88] (helo=mail.shareable.org) by monty-python.gnu.org with esmtps (TLS-1.0:DHE_RSA_AES_256_CBC_SHA:32) (Exim 4.52) id 1G7JAU-0000zs-Bz for qemu-devel@nongnu.org; Sun, 30 Jul 2006 17:49:50 -0400 Received: from mail.shareable.org (localhost [127.0.0.1]) by mail.shareable.org (8.12.11.20060308/8.12.11) with ESMTP id k6ULlCro007151 for ; Sun, 30 Jul 2006 22:47:12 +0100 Received: (from jamie@localhost) by mail.shareable.org (8.12.11.20060308/8.12.8/Submit) id k6ULlCEH007149 for qemu-devel@nongnu.org; Sun, 30 Jul 2006 22:47:12 +0100 Date: Sun, 30 Jul 2006 22:47:12 +0100 From: Jamie Lokier Subject: Re: [Qemu-devel] [RFC][PATCH] make sure disk writes actually hit disk Message-ID: <20060730214712.GB6255@mail.shareable.org> References: <44CA6B76.7000004@redhat.com> <44CB310B.9060308@bellard.org> <44CB77DF.9030700@redhat.com> <23bcb8700607291033q7ce66872j2ce2d830a8578dbc@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <23bcb8700607291033q7ce66872j2ce2d830a8578dbc@mail.gmail.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 Bill C. Riemers wrote: > How about compromising, and making the patch a run time option. > Presumably this is only a problem when the virtual machine is not > properly shutdown. For those ho want the extra security of knowing > the data will be written regardless of the shutdown status they can > enable the flag. By default it could be turned off. Then everybody > can be happy. Real disks don't provide that security unless you disable the disk's cache, or issue cache flush instructions to the disk. Modern guest OS filesystems are written with this in mind. With older guest OSes, you have to disable the disk cache if you want that kind of security with real disks. Is there any reason why the emulation should be any different? -- Jamie