From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christopher Smith Subject: Re: split RAID1 during backups? Date: Thu, 27 Oct 2005 10:04:02 +1000 Message-ID: <43601972.6020006@nighthawkrad.net> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Jeff Breidenbach Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids Jeff Breidenbach wrote: > Hi all, > [...] > So - I'm thinking of the following backup scenario. First, remount > /dev/md0 readonly just to be safe. Then mount the two component > paritions (sdc1, sdd1) readonly. Tell the webserver to work from one > component partition, and tell the backup process to work from the > other component partition. Once the backup is complete, point the > webserver back at /dev/md0, unmount the component partitions, then > switch read-write mode back on. Isn't this just the sort of scenario LVM snapshots are meant for ? It might not help with the duration aspect, but it will mean your services aren't down/non-redundant for the entire time it takes to backup. > Everything on this system seems bottlenecked by disk I/O. That > includes the rate web pages are served as well as the backup process > described above. While I'm always hungry for perforance tips, faster > backups are the current focus. For those interested in gory details > such as drive types, NCQ settings, kernel version and whatnot, I > dumped a copy of dmesg output here: http://www.jab.org/dmesg I think this might be one of those situations where SCSI really does offer a significant performance advantage, although if you're actually filling up that 500G, it'll be a quite a bit more expensive. See if you can get hold of a reasonably sized array using SCSI drives and do some comparitive benchmarking. You might also want to experiment with different filesystems, although that may not be feasible... CS