From mboxrd@z Thu Jan 1 00:00:00 1970 From: Richard Scobie Subject: Re: Software RAID 6 initial sync very slow Date: Mon, 02 Jun 2008 08:37:46 +1200 Message-ID: <4843089A.7040909@sauce.co.nz> References: <8CA91F18992AC9E-1724-EAF@webmail-ne13.sysops.aol.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <8CA91F18992AC9E-1724-EAF@webmail-ne13.sysops.aol.com> Sender: linux-raid-owner@vger.kernel.org To: thomas62186218@aol.com Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids thomas62186218@aol.com wrote: > My first test was to create a RAID 6 md device, 128K chunk, with all 12 > drives. The sync is currently underway at a very slow 30MB/sec, with > mdadm estimating this as a 9hr process. With an Adaptec 5805 RAID card > tested, I performed the RAID 6 initial sync with the same 12 drives in > just under 5 hours. Meanwhile, our total CPU usage during mdadm syncing > is at 5%, so there's plenty of CPU not being used. I have a very similar system, except single quad core and 16 x 750GB It syncs (md RAID6) in 3:40min which is roughly proportional to the time you see with your hardware RAID sync up, so you should be able to match it with md RAID. I cannot remember whether stripe_cache_size affected the sync time - currently I have this set to 16384. Regards, Richard