From mboxrd@z Thu Jan 1 00:00:00 1970 From: Brad Campbell Subject: Re: "Rebuild" speed on a forced resync Date: Fri, 14 Jan 2005 22:34:02 +0400 Message-ID: <41E8109A.7000603@wasp.net.au> References: <41E3A0B5.209@wasp.net.au> <16868.28778.598528.338592@cse.unsw.edu.au> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <16868.28778.598528.338592@cse.unsw.edu.au> Sender: linux-raid-owner@vger.kernel.org To: Neil Brown Cc: RAID Linux List-Id: linux-raid.ids Neil Brown wrote: > On Tuesday January 11, brad@wasp.net.au wrote: > >>G'day all, >> >>Just started my big raid using mdadm --update resync to ensure the parity blocks are A-OK after a >>kernel panic, and I have been monitoring my Disk IO with >>iostat -k 5 >> >>Now this is an average for a 5 second period. >>I note I'm seeing about 12,456 Kilobytes/sec from each drive, but a cat /proc mdstat is giving me >>6716 Kilobytes/sec. Given I'm doing a read consistency check I would expect an mdstat speed 9/10ths >>of my bulk per-drive read speed. (This array is sda -> sdj) >>Am I missing something really obvious? >> >>avg-cpu: %user %nice %sys %iowait %idle >> 39.18 0.00 60.82 0.00 0.00 >> >>Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn >>hda 0.00 0.00 0.00 0 0 >>sda 97.76 12465.67 0.00 33408 0 >>sdb 97.76 12465.67 0.00 33408 0 >>sdc 97.76 12465.67 0.00 33408 0 > > > So this is a 5 second sample... > In 5 seconds, 33408 kB were read. > That's 6681.6 kB/sec according to my calculator. > > So it looks like iostat is reporting something wrongly. I would look > there first. Ok, fair call on those stats. Having said that, we are talking 6.6 MB/sec per disk. Do I take it the /proc/mdstat figure of 6 MB/sec is not a total array rebuild speed, but a speed per array member? Regards, Brad