From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oliver Schinagl Subject: Expanding array with multiple devices Date: Thu, 28 Feb 2013 21:27:15 +0100 Message-ID: <512FBDA3.7080501@schinagl.nl> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids Hello list, I've looked online a bit, but didn't really find the answer to the following question. While expanding an existing raid is as simple as mdadm --add, followed by an mdadm --grow, How would you go about this when expanding it with multiple devices. A little bit of background. I have 8 2TB disks, 4 in a current raid5 array, which will be the donor disks en 4 'new' disk going to form the basis of a new array. I want to change chunk size and re-format to ext4 to a) optimize the new array according to the new parameters (stride,stripe-width) and (possibly) a new ondisk ext4 disk format (new features added since last time). The old array was 4 disk raid5, the new array will be 8 disk raid6. So far, I have created a new raid6 array with the 4 'new' disks + 2 'missing' for the parity. I have done it this way, so that I would have enough space to copy (and verify) files. having done a 4 disk raid6 without any missing devices, there would simply have not been enough space. True I could have used 3 data disks, 1 parity and 1 missing. Anyway, my plan next, is to expand the array. I can think of the following options. a) Remove 1 disk at a time from the old array, and add it to the new array, first 2 disks would be parity, after that --growing the last two. Big disadvantage is of course that there will be almost a week or two of re-syncing going on. b) Would be to somehow add all 'extra' disks at once, and have it rsync it all in one go. Any idea's how best to expand all this? Oliver