From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Robinson Subject: Speed up reshape? (was Re: Cancel reshape?) Date: Wed, 12 Jan 2011 05:53:40 +0000 Message-ID: <4D2D41E4.1000109@anonymous.org.uk> References: <4D2D2BD2.7000601@anonymous.org.uk> <4D2D32DF.9010002@anonymous.org.uk> <20110112163258.699a6fe0@notabene.brown> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20110112163258.699a6fe0@notabene.brown> Sender: linux-raid-owner@vger.kernel.org To: NeilBrown Cc: Linux RAID List-Id: linux-raid.ids On 12/01/2011 05:32, NeilBrown wrote: > On Wed, 12 Jan 2011 04:49:35 +0000 John Robinson > wrote: [...] >> Perhaps I can stop the reshape and restart it with the backup file >> elsewhere. Hmm, I've an SSD I haven't installed yet... Maybe time to >> give it a wee workout :-) > > That should work. > > mdadm --stop ... > copy file > mdadm --assemble ...... --backup-file=/new/place Yup. Not much of an improvement, though; the reshape is now running at ~10MB/s instead of ~6.5MB/s, so ~27 hours to go instead of ~40 hours. iostat tells me the original 3 discs are doing ~120 transactions per second, reading ~20MB/s and writing ~10MB/s, while the one new disc is doing ~60 tps, reading nothing (obviously) and writing ~10MB/s and the backup (SSD) is doing ~45 tps and writing ~20MB/s. ~120tps sounds about right for 120 seeks, 60 reads and 60 writes, and would explain the speed, but otherwise this looks odd to me - why are we reading ~60MB/s in total and writing ~40MB/s? I'd have expected to be reading less than we're writing. And why are we apparently reading and writing in blocks of under 512KB per device, when the backup file is 32MB? Is there something I can tweak to run the reshape in bigger chunks? sync_speed_min is already 200000... Currently running SystemRescueCD 2.0.0, 32-bit kernel 2.6.35 and mdadm 3.1.4. CPU usage is 2% system, 4% iowait. Cheers, John.