From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38746) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WBkwt-0005NB-6R for qemu-devel@nongnu.org; Fri, 07 Feb 2014 07:54:34 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WBkwl-00024R-Q1 for qemu-devel@nongnu.org; Fri, 07 Feb 2014 07:54:27 -0500 Received: from mx.beyond.pl ([92.43.117.49]:36801) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WBkwl-00024N-JJ for qemu-devel@nongnu.org; Fri, 07 Feb 2014 07:54:19 -0500 Message-ID: <52F4D778.6070001@beyond.pl> Date: Fri, 07 Feb 2014 13:54:16 +0100 From: =?UTF-8?B?TWFyY2luIEdpYnXFgmE=?= MIME-Version: 1.0 References: <52F46298.8020602@ozlabs.ru> <52F48F3A.40606@redhat.com> <52F4CD3E.1000809@ozlabs.ru> <52F4D5C6.1050206@redhat.com> In-Reply-To: <52F4D5C6.1050206@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] migration question: disk images on nfs server List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Orit Wasserman , Alexey Kardashevskiy , qemu-devel@nongnu.org > It is more a NFS issue, if you have a file in NFS that two users in > two different host are accessing (one at least write to it) you will > need to enforce the "sync" option. > Even if you flush all the data and close the file the NFS client can still > have cached data that it didn't sync to the server. Do you know if is applies to linux O_DIRECT writes as well? From comment in fs/nfs/direct.c: * When an application requests uncached I/O, all read and write requests * are made directly to the server; data stored or fetched via these * requests is not cached in the Linux page cache. The client does not * correct unaligned requests from applications. All requested bytes are * held on permanent storage before a direct write system call returns to * an application. -- mg