From mboxrd@z Thu Jan 1 00:00:00 1970 From: "NeilBrown" Subject: Re: [PATCH 00/18] Assorted md patches headed for 2.6.30 Date: Thu, 12 Feb 2009 21:45:38 +1100 (EST) Message-ID: <780b8d5e33de8ec127222529e84f6026.squirrel@neil.brown.name> References: <20090212031009.23983.14496.stgit@notabene.brown> <20090212081148.GD9439@rap.rap.dk> <12039e3b9172d1a1347b8396cab59f11.squirrel@neil.brown.name> <20090212095305.GB11981@rap.rap.dk> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20090212095305.GB11981@rap.rap.dk> Sender: linux-raid-owner@vger.kernel.org To: Keld =?iso-8859-1?Q?J=F8rn_Simonsen?= Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On Thu, February 12, 2009 8:53 pm, Keld J=F8rn Simonsen wrote: > On Thu, Feb 12, 2009 at 08:21:12PM +1100, NeilBrown wrote: >> On Thu, February 12, 2009 7:11 pm, Keld J=F8rn Simonsen wrote: >> > On Thu, Feb 12, 2009 at 02:10:10PM +1100, NeilBrown wrote: >> >> Comments and testing very welcome. >> > >> > I would rather have functionality to convert raid10 to raid5. >> > raid1 should be depreciated, as raid10,n2 for all purposes is the = same >> > but better implementation and performance, and raid10,f2 and raid1= 0,o2 >> > are even better. Nobody should use raid1 anymore. >> >> That is a fairly simplistic view. > > It was also formulated to provoke some thoughts. > >> raid1 supports --write-mostly and --write-behind which raid10 is >> unlikely >> ever to support. > > why? > > Anyway would it not be possible that this functionality be implemente= d > for raid10,n2? It would be possible, but it might not be sensible. write-mostly and write-behind only really make sense when you have the clear distinction between drives that raid1 gives you. These options don't make sense for raid10 in general. Only in very spe= cific layouts. If you like, raid1 is an implementation of a specific raid10 layout, where it makes sense to add some extra functionality. > > Some code to grow raid10 would also be desirable. Maybe it is some of > the same operations that need to be applied: getting the old data in, > have it restructured for the new format, in a safe way, and possibly > with the help of an extra disk, or possibly not. It sounds non-trivia= l > to me too. What particular growth scenarios are you interested it? Just adding a drive and restriping onto that? i.e keep that same nominal layout but increase 'raid-disks'? That would be quite similar to the raid5 grow operation so it shouldn't be too hard to achieve. A 'grow' which changed the layout (e.g. near to far) would be a lot harder. NeilBrown -- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html