From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: xfs > md 50% write performance drop on .30+ kernel? Date: Tue, 13 Oct 2009 18:52:41 -0400 Message-ID: <20091013225241.GA32197@infradead.org> References: <66781b10910120958k4afb637ejba79e4c23900c4da@mail.gmail.com> <20091013013352.GA24869@infradead.org> <66781b10910130406s4119985fg5db7679a2e9fd4f2@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <66781b10910130406s4119985fg5db7679a2e9fd4f2@mail.gmail.com> Sender: linux-raid-owner@vger.kernel.org To: mark delfman Cc: Linux RAID Mailing List List-Id: linux-raid.ids On Tue, Oct 13, 2009 at 12:06:24PM +0100, mark delfman wrote: > A little more information which I ?think? seems to point at MD..... > > Creating an EXT3 FS on an MD RAID also shows a circa 50% performance drop. > We have tried a multitude of RAID options (raid6/0 various chunks etc). > > Using a hardware based raid XFS / EXT3 shows no performance drop > (although the hardware raid is significantly slower than MD in the > first place) > > We are happy to keep testing and offering anything that could be > useful, we are just a little stuck thinking of anything else to do.... Can you test with conv=direct added to the dd command lines? If that shows the problems too it's probably writeback-related. If not the problems must be somewhere lower in the stack.