From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konstantin Svist Subject: Re: Changing Chunk Size on Array Date: Mon, 19 Jul 2010 17:17:14 -0700 Message-ID: <4C44EB0A.2060604@gmail.com> References: <20100720014955.529eb9ca@notabene> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20100720014955.529eb9ca@notabene> Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 07/19/2010 04:49 PM, Neil Brown wrote: > On Sat, 17 Jul 2010 16:15:55 -0500 > "Leslie Rhorer" wrote: > >> I'm thinking about changing the chunk size on one of my arrays in >> order to potentially improve performance. The man page rather suggests -c >> is a vlaid option under Grow mode, although it doesn't specifically say >> mdadm supports it under --grow. Is it indeed supported under mdadm 2.6.7.2 >> and kernel 2.6.26-2? Assuming so, I would like to know a bit more about the >> change before issuing the command. Speficialy, what are the details of the >> process? Does the entire (RAID 6) array have to be re-written, such as is >> the case with adding a drive to the array? Does the recovery start >> immediately? Can it be interrupted and then continue at a later time? > Yes, you can change chunksize with --grow. > I think you need mdadm-3.1.2 and kernel 2.6.32 though (version numbers might > not be accurate, but are close). > > Yes, the entire array gets re-written just like adding an extra device. > The reshape does start immediately. > If you shutdown or crash, then on restart the reshape will pick up where it > left off. I ran mine with mdadm v3.1.2 on 2.6.33.6-147.fc13.x86_64 (Fedora) Too bad I screwed up the FS by shrinking the array too much beforehand - now I have no idea whether it would've worked or not.