From mboxrd@z Thu Jan 1 00:00:00 1970 From: david@lang.hm Subject: Re: limits on raid Date: Mon, 18 Jun 2007 10:28:38 -0700 (PDT) Message-ID: References: <18034.479.256870.600360@notabene.brown> <18034.3676.477575.490448@notabene.brown> <20070616020320.GB2002@animx.eu.org> <18035.23867.576212.859440@notabene.brown> <4676BEC2.7090809@redhat.com> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Return-path: In-Reply-To: <4676BEC2.7090809@redhat.com> Sender: linux-kernel-owner@vger.kernel.org To: Brendan Conoboy Cc: Neil Brown , Wakko Warner , linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org List-Id: linux-raid.ids On Mon, 18 Jun 2007, Brendan Conoboy wrote: > david@lang.hm wrote: >> in my case it takes 2+ days to resync the array before I can do any >> performance testing with it. for some reason it's only doing the rebuild >> at ~5M/sec (even though I've increased the min and max rebuild speeds and >> a dd to the array seems to be ~44M/sec, even during the rebuild) > > With performance like that, it sounds like you're saturating a bus somewhere > along the line. If you're using scsi, for instance, it's very easy for a > long chain of drives to overwhelm a channel. You might also want to consider > some other RAID layouts like 1+0 or 5+0 depending upon your space vs. > reliability needs. I plan to test the different configurations. however, if I was saturating the bus with the reconstruct how can I fire off a dd if=/dev/zero of=/mnt/test and get ~45M/sec whild only slowing the reconstruct to ~4M/sec? I'm putting 10x as much data through the bus at that point, it would seem to proove that it's not the bus that's saturated. David Lang