From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Brown Subject: Re: Changing Chunk Size on Array Date: Tue, 20 Jul 2010 01:49:55 +0200 Message-ID: <20100720014955.529eb9ca@notabene> References: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Leslie Rhorer Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids 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. NeilBrown