From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Brown Subject: Re: potentially lost largeish raid5 array.. Date: Sat, 24 Sep 2011 17:16:40 +0200 Message-ID: References: <201109221950.36910.tfjellstrom@shaw.ca> <201109231022.59437.tfjellstrom@shaw.ca> <4E7D152C.9080704@hardwarefreak.com> <201109231811.08061.tfjellstrom@shaw.ca> <4E7DCA66.4000705@hardwarefreak.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4E7DCA66.4000705@hardwarefreak.com> Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 24/09/2011 14:17, Stan Hoeppner wrote: > On 9/23/2011 7:11 PM, Thomas Fjellstrom wrote: >> On September 23, 2011, Stan Hoeppner wrote: > >>> When properly configured XFS will achieve near spindle throughput. >>> Recent versions of mkfs.xfs read the mdraid configuration and configure >>> the filesystem automatically for sw, swidth, number of allocation >>> groups, etc. Thus you should get max performance out of the gate. >> >> What happens when you add a drive and reshape? Is it enough just to >> tweak the >> mount options? > > When you change the number of effective spindles with a reshape, and > thus the stripe width and stripe size, you definitely should add the > appropriate XFS mount options and values to reflect this. Performance > will be less than optimal if you don't. > > If you use a linear concat under XFS you never have to worry about the > above situation. It has many other advantages over a striped array and > better performance for many workloads, especially multi user general > file serving and maildir storage--workloads with lots of concurrent IO. > If you 'need' maximum single stream performance for large files, a > striped array is obviously better. Most applications however don't need > large single stream performance. > If you use a linear concatenation of drives for XFS, is it not correct that you want one allocation group per drive (or per raid set, if you are concatenating a bunch of raid sets)? If you then add another drive or raid set, can you grow XFS with another allocation group? mvh., David