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: Fri, 24 Apr 2009 01:34:02 +0200 Message-ID: <49F0FAEA.2020904@wpkg.org> References: <49EF6DF7.9020406@wpkg.org> <1240512313.28015.14.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: <1240512313.28015.14.camel@think.oraclecorp.com> List-ID: 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? > But, tuning > for this config is something we have to concentrate more on. > >> - taking snapshots of individual files (file images on SAN) is not >> possible with btrfs? Probably they would have to be placed in separate >> directories first to make snapshots - some minor manageability issue > > Btrfs can't snapshot a single dir, but it can snapshot a single file. > See the bcp command included with btrfs-progs. > > I'd also suggest using preallocated files (via fallocate) instead of > sparse files. I will perform better in general. When performance is needed - sure. -- Tomasz Chmielewski http://wpkg.org