From mboxrd@z Thu Jan 1 00:00:00 1970 From: mark delfman Subject: Re: xfs > md 50% write performance drop on .30+ kernel? Date: Wed, 14 Oct 2009 20:34:38 +0100 Message-ID: <66781b10910141234h5fbf5ac3k4adc347621dbc2a1@mail.gmail.com> References: <66781b10910120958k4afb637ejba79e4c23900c4da@mail.gmail.com> <20091013013352.GA24869@infradead.org> <66781b10910130406s4119985fg5db7679a2e9fd4f2@mail.gmail.com> <20091013225241.GA32197@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20091013225241.GA32197@infradead.org> Sender: linux-raid-owner@vger.kernel.org To: Christoph Hellwig Cc: Linux RAID Mailing List List-Id: linux-raid.ids Hi Chris... we tried the direct DD as requested and the problem is still there... 1.3GBsec > 325MBsec (even more dromatic)... hopefully this helps narrow it down? Write > MD linux-poly:~ # dd if=3D/dev/zero of=3D/dev/md0 oflag=3Ddirect bs=3D1M c= ount=3D20000 20000+0 records in 20000+0 records out 20971520000 bytes (21 GB) copied, 15.7671 s, 1.3 GB/s Write > XFS > MD linux-poly:~ # dd if=3D/dev/zero of=3D/mnt/md0/test oflag=3Ddirect bs=3D= 1M count=3D20000 20000+0 records in 20000+0 records out 20971520000 bytes (21 GB) copied, 64.616 s, 325 MB/s On Tue, Oct 13, 2009 at 11:52 PM, Christoph Hellwig = wrote: > 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 et= c). >> >> 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..= =2E. > > Can you test with conv=3Ddirect added to the dd command lines? =A0If = that > shows the problems too it's probably writeback-related. =A0If not the > problems must be somewhere lower in the stack. > -- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html