From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andreas Hirstius Date: Wed, 06 Apr 2005 07:30:37 +0000 Subject: Re: [Gelato-technical] Serious performance degradation on a RAID Message-Id: <4253901D.8030002@cern.ch> List-Id: References: <16978.62532.841151.100745@napali.hpl.hp.com> In-Reply-To: <16978.62532.841151.100745@napali.hpl.hp.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org Rob Fowler wrote: > I've recently had discussions with several vendors who have mentioned > similar magnitudes of disk performance degradation due to the > coupling of vibration between cooling fans and disks. This can > dramatically increase seek time by keeping the arm from settling. > In one case, upgrading a chassis fan caused disk throughput to go down > by a factor of 16. The solution is careful attention to vibration > damping in mountings. Vibration caused by fan bearing wear could have > a similar effect. > We've also seen similiar problems before... So I made sure it's not something "mechanical" ;-) > Can you go back to your old kernel to verify that it is still > giving you the same performance? > I'm constantly going back and forth between "working" and "not working" kernels. The performance with a given kernel doesn't change... Andreas > -- Rob Fowler > > > David Mosberger wrote: > >>>>>>> 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 >> >> _______________________________________________ >> Gelato-technical mailing list >> Gelato-technical@gelato.unsw.edu.au >> https://www.gelato.unsw.edu.au/mailman/listinfo/gelato-technical > >