From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=51796 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OoGZW-0001mF-Jk for qemu-devel@nongnu.org; Wed, 25 Aug 2010 10:03:24 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OoGZV-0005Q0-2D for qemu-devel@nongnu.org; Wed, 25 Aug 2010 10:03:22 -0400 Received: from mx1.redhat.com ([209.132.183.28]:27647) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OoGZU-0005Pj-PJ for qemu-devel@nongnu.org; Wed, 25 Aug 2010 10:03:21 -0400 Message-ID: <4C75229C.50406@redhat.com> Date: Wed, 25 Aug 2010 17:03:08 +0300 From: Avi Kivity MIME-Version: 1.0 References: <1282646430-5777-1-git-send-email-kwolf@redhat.com> <4C73C2BF.8050300@codemonkey.ws> <4C73C622.7080808@redhat.com> <4C73C926.3010901@codemonkey.ws> <4C73C9CF.7090800@redhat.com> <4C73CAA9.2060104@codemonkey.ws> <4C73CB85.9010306@redhat.com> <4C73CBD6.7000900@codemonkey.ws> <4C73CCCB.6050704@redhat.com> <4C73CF8D.5060405@codemonkey.ws> <4C74C2F3.9050506@redhat.com> <4C7510C1.8080305@codemonkey.ws> <4C75195A.8050508@redhat.com> <4C751EA7.6050406@codemonkey.ws> In-Reply-To: <4C751EA7.6050406@codemonkey.ws> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] Re: [RFC][STABLE 0.13] Revert "qcow2: Use bdrv_(p)write_sync for metadata writes" List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: Kevin Wolf , stefanha@gmail.com, mjt@tls.msk.ru, qemu-devel@nongnu.org, hch@lst.de On 08/25/2010 04:46 PM, Anthony Liguori wrote: > On 08/25/2010 08:23 AM, Avi Kivity wrote: >> On 08/25/2010 03:46 PM, Anthony Liguori wrote: >>> >>> If we had another disk format that only supported growth and >>> metadata for a backing file, can you think of another failure scenario? >> >> btw, only supporting growth is a step backwards. Currently >> file-backed disks keep growing even the guest-used storage doesn't >> grow, since once we allocate something we never release it. But >> eventually guests will start using TRIM or DISCARD or however it's >> called, and then we can expose it and reclaim unused blocks. > > BTW, something that had the features of qcow2 that people actually > used andwas fully asynchronous, performed well, and had a high degree > of confidence in data integrity would be a major step forward, not > backwards. > TRIM/DISCARD is not a feature that people use (esp. as it's not available) but we do want to support it in our image formats. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.