From mboxrd@z Thu Jan 1 00:00:00 1970 From: "NeilBrown" Subject: Re: reshape raid5 to raid6 Date: Thu, 9 Jul 2009 19:35:05 +1000 (EST) Message-ID: <0bd56967e395ec8488de00126f297b86.squirrel@neil.brown.name> References: <20090624102729.GY2828@rlogin.dk> <972c997a386db1106868b3dc6b29ee21.squirrel@neil.brown.name> 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: Mikael Abrahamsson Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On Thu, July 9, 2009 6:36 pm, Mikael Abrahamsson wrote: > On Wed, 24 Jun 2009, Beolach wrote: > >> If a raid5 is changed to raid6, and then the raid6 is grown w/ >> additional disks, will that switch it to a more traditional layout, >> since it has to be re-striped anyway? > > I'd greatly appreciate if someone in the know could answer this? Sorry, I thought I had... must have only intended to. The answer is "only if you explicitly tell it to", which mdadm-3.1 will do for you. If you switch to raid6 by writing to a sysfs file, then grow with an earlier version of mdadm, it will keep to unusual layout. > > Also, this raid6 with all Q blocks on a single drive, will older kernels > read this as well or is 2.6.30 needed to handle this "new" layout? You will need 2.6.30. Older kernels will not understand it. > > I'd like to convert a raid5 to raid6 with 2.6.30, then go back to 2.6.28 > and run it, then when I grow it next time, I'd like to get the "correct" > layout with the Q blocks striped just as if I had created the raid6 from > scratch. Is this possible? Nope, sorry. NeilBrown