From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dexter Filmore Subject: Re: raid5 resize in 2.6.17 - how will it be different from raidreconf? Date: Mon, 22 May 2006 13:17:36 +0200 Message-ID: <200605221317.37083.Dexter.Filmore@gmx.de> References: <200605220034.49858.Dexter.Filmore@gmx.de> <17520.61194.529436.322401@cse.unsw.edu.au> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <17520.61194.529436.322401@cse.unsw.edu.au> Content-Disposition: inline Sender: linux-raid-owner@vger.kernel.org To: Neil Brown Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids > > Will it be less risky to grow an array that way? > > It should be. In particular it will survive an unexpected reboot (as > long as you don't lose and drives at the same time) which I don't > think raidreconf would. > Testing results so far are quite positive. Write cache comes to mind - did you test power fail scenarios? > > (And while talking of that: can I add for example two disks and grow > > *and* migrate to raid6 in one sweep or will I have to go raid6 and then > > add more disks?) > > Adding two disks would be the preferred way to do it. > Add only one disk and going to raid6 is problematic because the > reshape process will be over-writing live data the whole time, making > crash protection quite expensive. > By contrast, when you are expanding the size of the array, after the > first few stripes you are writing to an area of the drives where there > is no live data. Let me see if I got this right: if I add *two* disks and go from raid 5 to 6 with raidreconf, no live data needs to be overwritten and in case something fails I will still be able to assemble the "old" array..? -- -----BEGIN GEEK CODE BLOCK----- Version: 3.12 GCS d--(+)@ s-:+ a- C+++(++++) UL+>++++ P+>++ L+++>++++ E-- W++ N o? K- w--(---) !O M+ V- PS++(+) PE(-) Y++ PGP t++(---)@ 5 X+(++) R+(++) tv--(+)@ b++(+++) DI+++ D G++ e* h>++ r%>* y? ------END GEEK CODE BLOCK------ http://www.stop1984.com http://www.againsttcpa.com