From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bill Davidsen Subject: Re: Slow(?) raid5 to raid6 reshape speed Date: Tue, 16 Feb 2010 12:34:48 -0500 Message-ID: <4B7AD738.6080503@tmr.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Michael Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids Michael wrote: > Hello, > > iam reshaping my 4-drive raid5 to a 5-drive raid6, but the speed is a > little slow. > > md2 : active raid6 sdc3[0] sdg3[4] sdf3[3] sda3[2] sdd3[1] > 2898182016 blocks super 0.91 level 6, 64k chunk, algorithm 18 [5/4] > [UUUU_] > [======>..............] reshape = 34.2% (330530816/966060672) > finish=2897.5min speed=3655K/sec > > i know it is a expensive process, but my system near-to-idle, so there may > be something wrong. > with top, i can see there is no noticable cpu load caused by the md2_raid6 > process or any other. > with iotop, i can see mdadm reading and writing a little data once a > secound, but not continuous. > > i think the kernel's raid io is not visible at iotop or iam wrong? > > i have moved the --backup-file from my usb drive to a internal ide hard > drive and gained 800k/sec more speed. > ~3000-4000k/sec are not so bad that the reshaping takes forever, but could > be faster, right? > > i have tried playing around with sync_speed_min and sync_speed_max without > any result. > setting the stripe_cache to 8192 or something did not show a real > performance gain. > > You can go larger than that, double it or try 32k. I have heard reports of evil at 64k, I wouldn't go there other than with test data. > is my speed bad, good, normal? any ideas how to "tune" it a bit? > -- Bill Davidsen "We can't solve today's problems by using the same thinking we used in creating them." - Einstein