From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tomasz Chmielewski Subject: Re: LVM vs btrfs as a "volume manager" for SANs Date: Thu, 02 Jul 2009 17:22:24 +0200 Message-ID: <4A4CD0B0.2080907@wpkg.org> References: <49EF6DF7.9020406@wpkg.org> <1240512313.28015.14.camel@think.oraclecorp.com> <49F0FAEA.2020904@wpkg.org> <1240576718.29896.2.camel@think.oraclecorp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Cc: linux-btrfs@vger.kernel.org To: Chris Mason Return-path: In-Reply-To: <1240576718.29896.2.camel@think.oraclecorp.com> List-ID: Chris Mason wrote: > On Fri, 2009-04-24 at 01:34 +0200, Tomasz Chmielewski wrote: >> Chris Mason schrieb: >> >>>> However, with btrfs, I'm not sure about: >>>> >>>> - what happens if SAN machine crashes while the iSCSI file images were >>>> being written to; with LVM and its block devices, I'm somehow more >>>> confident it wouldn't make more data loss than necessary >>> If iscsi is writing with O_DIRECT|O_SYNC it should work. >> What if it doesn't? >> > > Writes would go to the page cache only (not O_DIRECT) and the metadata > wouldn't get flushed with each write (not O_SYNC). What about the "administrative" part of using btrfs as a volume manager? For example, I can partition (fdisk + kpartx), extend volumes in LVM easily, on the host. Are there any tools to "partition" or "extend" file images? qemu-nbd and nbd-client come to mind, but it's a bit of an overhead (in typing, I mean). -- Tomasz Chmielewski http://wpkg.org