From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: Re: potentially lost largeish raid5 array.. Date: Sun, 25 Sep 2011 19:37:47 +1000 Message-ID: <20110925193747.074d965b@notabene.brown> References: <201109221950.36910.tfjellstrom@shaw.ca> <201109230209.36209.thomas@fjellstrom.ca> <20110923191539.110b7be1@notabene.brown> <201109231026.53770.thomas@fjellstrom.ca> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/qyvdUz7gHFu4V9XVuHEYh1d"; protocol="application/pgp-signature" Return-path: In-Reply-To: <201109231026.53770.thomas@fjellstrom.ca> Sender: linux-raid-owner@vger.kernel.org To: thomas@fjellstrom.ca Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids --Sig_/qyvdUz7gHFu4V9XVuHEYh1d Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Fri, 23 Sep 2011 10:26:53 -0600 Thomas Fjellstrom wrote: > On September 23, 2011, NeilBrown wrote: > > On Fri, 23 Sep 2011 02:09:36 -0600 Thomas Fjellstrom > >=20 > > wrote: > > > I forgot to say, but: Thank you very much :) for the help, and your > > > tireless work on md. > >=20 > > You've very welcome .... but I felt I needed to respond to that word > > "tireless". > > The truth is that I am getting rather tired of md .... if anyone knows > > anyone who wants to get into kernel development and is wondering where = to > > start - please consider whispering 'the md driver' in their ear. Plenty > > to do, great mentoring possibilities, and competent linux kernel engine= ers > > with good experience are unlikely to have much trouble finding a job ;-) > >=20 > > NeilBrown >=20 > Very tempting. How much work do you think it would be to add in full raid= 10=20 > reshape support? ;D (not that I'm volunteering, I don't think I could=20 > comprehend a lot of the raid code, at least not at this point in time =20 > (extenuating circumstances)). >=20 RAID10 reshape is more complicated than RAID5/6 reshape because there are more options - more combinations. So you would probably implement a subset of possible reshapes. And then maybe implement another subset. Providing you have: - a clear understanding of the intermediate state and a way to record that state in the metadata - a way to tell if a given block is in the 'old' layout or the 'new' layo= ut or 'being reshaped' - somewhere in memory to store all the blocks that are 'being reshaped' it should be fairly easy. RAID5/6 has a stripe-cache so the last point is trivial. Handling that in RAID10 is probably the biggest single part of the task. So: not a trivial task, but not an enormous task either.... which doesn't narrow it down very much I guess. NeilBrown --Sig_/qyvdUz7gHFu4V9XVuHEYh1d Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (GNU/Linux) iD8DBQFOfvZrG5fc6gV+Wb0RAiGRAJ9GzrX5bP5InkXXkxSMyJdB2G/gGQCgt8mm HHwRi3QavxIOxC/kFLJET20= =9dBp -----END PGP SIGNATURE----- --Sig_/qyvdUz7gHFu4V9XVuHEYh1d--