From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Brown Subject: Re: Change Chunk Size on Array? Date: Wed, 13 May 2009 14:45:47 +1000 Message-ID: <18954.20603.952706.467047@notabene.brown> References: <16137381.post@talk.nabble.com> <23514897.post@talk.nabble.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: message from SandeepKsinha on Tuesday May 12 Sender: linux-raid-owner@vger.kernel.org To: SandeepKsinha Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On Tuesday May 12, sandeepksinha@gmail.com wrote: > > > > crshman wrote: > > > > Hello All, > > > > I wanted to know if it were possible to change the chunk size on an array > > after it has been created. I have a software raid 5 comprised of 7 drives > > with a chunk size of 64k. I wanted to up that to 1024k, would this be > > possible without losing any data? This isn't mission critical so it is ok > > if i need to stop the array first, however I'd rather not lose any data. > > > It is possible to change the chunksize but for the same you would need to > offline your array. Is it? How? Online changing of chunk size for raid5 is very close to being implemented. All the kernel side support will be in 2.6.30. I just need to spend some time getting mdadm to make it work. Because data is being rearranged in-place, and because you don't want to lose everything if your systems crashes, mdadm will have to work in tandem with the kernel making a backup copy of a section of the array, allowing the kernel to reshape that section, and then moving on to the next section. It will be slow, but it will be reliable. NeilBrown