From mboxrd@z Thu Jan 1 00:00:00 1970 From: david@lang.hm Subject: Re: limits on raid Date: Tue, 19 Jun 2007 13:51:36 -0700 (PDT) Message-ID: References: <4676BEC2.7090809@redhat.com> <20070618180327.GP10008@csclub.uwaterloo.ca> <20070618183324.GL10006@csclub.uwaterloo.ca> <4676D8DE.3050903@redhat.com> <20070618214633.GA15468@animx.eu.org> <20070619201111.GQ10008@csclub.uwaterloo.ca> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Return-path: In-Reply-To: <20070619201111.GQ10008@csclub.uwaterloo.ca> Sender: linux-raid-owner@vger.kernel.org To: Lennart Sorensen Cc: Wakko Warner , Brendan Conoboy , Neil Brown , linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org List-Id: linux-raid.ids On Tue, 19 Jun 2007, Lennart Sorensen wrote: > On Mon, Jun 18, 2007 at 02:56:10PM -0700, david@lang.hm wrote: >> yes, I'm useing promise drive shelves, I have them configured to export >> the 15 drives as 15 LUNs on a single ID. >> >> I'm going to be useing this as a huge circular buffer that will just be >> overwritten eventually 99% of the time, but once in a while I will need to >> go back into the buffer and extract and process the data. > > I would guess that if you ran 15 drives per channel on 3 different > channels, you would resync in 1/3 the time. Well unless you end up > saturating the PCI bus instead. > > hardware raid of course has an advantage there in that it doesn't have > to go across the bus to do the work (although if you put 45 drives on > one scsi channel on hardware raid, it will still be limited). I fully realize that the channel will be the bottleneck, I just didn't understand what /proc/mdstat was telling me. I thought that it was telling me that the resync was processing 5M/sec, not that it was writing 5M/sec on each of the two parity locations. David Lang