From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bill Davidsen Subject: Re: Where is the performance bottleneck? Date: Wed, 28 Sep 2005 16:04:47 -0400 Message-ID: <433AF75F.2060208@tmr.com> References: <200508302305.j7UN5bE23350@www.watkins-home.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <200508302305.j7UN5bE23350@www.watkins-home.com> Sender: linux-raid-owner@vger.kernel.org To: Guy Cc: 'Holger Kiehl' , 'Mark Hahn' , 'linux-raid' , 'linux-kernel' List-Id: linux-raid.ids Guy wrote: >In most of your results, your CPU usage is very high. Once you get to about >90% usage, you really can't do much else, unless you can improve the CPU >usage. > That seems one of the problems with software RAID, the calculations are done in the CPU and not dedicated hardware. As you move to the top end drive hardware the CPU gets to be a limit. I don't remember off the top of my head how threaded this code is, and if more CPUs will help. I see you are using RAID-1 for your system stuff, did one of the tests use RAID-0 over all the drives? Mirroring or XOR redundancy help stability but hurt performance. Was the 270MB/s with RAID-0 or ??? -- bill davidsen CTO TMR Associates, Inc Doing interesting things with small computers since 1979