From mboxrd@z Thu Jan 1 00:00:00 1970 From: Richard Scobie Subject: Re: raid5 grow reshaping speed is unchangeable Date: Sat, 29 Dec 2007 17:38:12 +1300 Message-ID: <4775CF34.7030400@sauce.co.nz> References: <380-2200712528192139967@mochamail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <380-2200712528192139967@mochamail.com> Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids Cody Yellan wrote: > You are right, Richard. RHEL5 had a stripe_cache_size of 256 when > the reshape began. I increased it to 1024 and the reshape speed > doubled to 4500K/s. I did not see any increase in memory usage. I > tried 2048 and then 4096 but saw no difference in speed. Sorry, I did not make myself clear. Back when I was seeing the slow resync speeds, it was due to larger than default stripe_cache_size - I had increased to 16384. When this was reduced back to the default, which I suspect is 256, speeds were back up to more normal levels - much faster than the 4.5MB/s you are seeing. At some point, this issue was fixed and currently on 2.6.22, with a stripe_cache_size of 16384 and a 4 x 500GB SATA II md RAID 5, resync speed is 162MB/s. Perhaps somthing different occurs on a reshape, (which I have only now realised you were doing). Regards, Richard