From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Mosberger Date: Tue, 05 Apr 2005 20:25:40 +0000 Subject: Re: [Gelato-technical] Serious performance degradation on a RAID with Message-Id: <16978.62532.841151.100745@napali.hpl.hp.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org >>>>> On Tue, 05 Apr 2005 20:11:51 +0200, Andreas Hirstius said: Andreas> Hi, We have a rx4640 with 3x 3Ware 9500 SATA controllers Andreas> and 24x WD740GD HDD in a software RAID0 configuration Andreas> (using md). With kernel 2.6.11 the read performance on the Andreas> md is reduced by a factor of 20 (!!) compared to previous Andreas> kernels. The write rate to the md doesn't change!! (it Andreas> actually improves a bit). Is there any reason to believe this change in behavior is ia64-specific? I doubt it. The q-syscollect profiles on your web-site shows that the CPU is basically completely idle. You may want to try 2.6.10 to see whether the bad behavior was introduced before or after that. Unfortunately, 2.6 is developing very rapidly so you may have to do more binary searching between 2.6.9 and 2.6.10 or 2.6.10 and 2.6.11 to pin the problem down to a useful granularity. You may also want to look at the bitkeeper changelogs to see if you can find anything suspicious (you can do that easily via the web by browsing the source code [1]). Lastly, you may want to ask on linux-kernel whether anybody can think of a change that could have this effect. --david [1] http://linux.bkbits.net:8080/linux-2.5/src?nav=index.html