From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: Notes on block I/O data integrity Date: Tue, 25 Aug 2009 21:36:21 +0200 Message-ID: <20090825193621.GA19778@lst.de> References: <20090825181120.GA4863@lst.de> <90eb1dc70908251233m4b90ddfuabb4d26bccd62c63@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Christoph Hellwig , qemu-devel@nongnu.org, kvm@vger.kernel.org, rusty@rustcorp.com.au To: Javier Guerra Return-path: Received: from verein.lst.de ([213.95.11.210]:57506 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755725AbZHYTgb (ORCPT ); Tue, 25 Aug 2009 15:36:31 -0400 Content-Disposition: inline In-Reply-To: <90eb1dc70908251233m4b90ddfuabb4d26bccd62c63@mail.gmail.com> Sender: kvm-owner@vger.kernel.org List-ID: On Tue, Aug 25, 2009 at 02:33:30PM -0500, Javier Guerra wrote: > On Tue, Aug 25, 2009 at 1:11 PM, Christoph Hellwig wrote: > > ??- barrier requests and cache flushes are supported by all local > > ?? disk filesystem in popular use (btrfs, ext3, ext4, reiserfs, XFS). > > ?? However unlike the other filesystems ext3 does _NOT_ enable barriers > > ?? and cache flush requests by default. > > what about LVM? iv'e read somewhere that it used to just eat barriers > used by XFS, making it less safe than simple partitions. Oh, any additional layers open another by cans of worms. On Linux until very recently using LVM or software raid means only disabled write caches are safe. From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1Mg1ol-0005aJ-FJ for qemu-devel@nongnu.org; Tue, 25 Aug 2009 15:36:31 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1Mg1og-0005YA-Rv for qemu-devel@nongnu.org; Tue, 25 Aug 2009 15:36:30 -0400 Received: from [199.232.76.173] (port=48308 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Mg1og-0005Y5-Gy for qemu-devel@nongnu.org; Tue, 25 Aug 2009 15:36:26 -0400 Received: from verein.lst.de ([213.95.11.210]:34816) by monty-python.gnu.org with esmtps (TLS-1.0:DHE_RSA_3DES_EDE_CBC_SHA1:24) (Exim 4.60) (envelope-from ) id 1Mg1of-0006hh-Sz for qemu-devel@nongnu.org; Tue, 25 Aug 2009 15:36:26 -0400 Date: Tue, 25 Aug 2009 21:36:21 +0200 From: Christoph Hellwig Message-ID: <20090825193621.GA19778@lst.de> References: <20090825181120.GA4863@lst.de> <90eb1dc70908251233m4b90ddfuabb4d26bccd62c63@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <90eb1dc70908251233m4b90ddfuabb4d26bccd62c63@mail.gmail.com> Subject: [Qemu-devel] Re: Notes on block I/O data integrity List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Javier Guerra Cc: rusty@rustcorp.com.au, Christoph Hellwig , kvm@vger.kernel.org, qemu-devel@nongnu.org On Tue, Aug 25, 2009 at 02:33:30PM -0500, Javier Guerra wrote: > On Tue, Aug 25, 2009 at 1:11 PM, Christoph Hellwig wrote: > > ??- barrier requests and cache flushes are supported by all local > > ?? disk filesystem in popular use (btrfs, ext3, ext4, reiserfs, XFS). > > ?? However unlike the other filesystems ext3 does _NOT_ enable barriers > > ?? and cache flush requests by default. > > what about LVM? iv'e read somewhere that it used to just eat barriers > used by XFS, making it less safe than simple partitions. Oh, any additional layers open another by cans of worms. On Linux until very recently using LVM or software raid means only disabled write caches are safe.