From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Clements Subject: Re: [ANNOUNCE][PATCH 2.6] md: persistent (file-backed) bitmap and async writes Date: Thu, 17 Jun 2004 13:57:13 -0400 Sender: linux-raid-owner@vger.kernel.org Message-ID: <40D1DB79.5080507@steeleye.com> References: <40198E85.29EBC8E0@SteelEye.com> <16422.62911.755570.855200@notabene.cse.unsw.edu.au> <4027E342.D02202F1@SteelEye.com> <16424.8182.876520.280031@notabene.cse.unsw.edu.au> <402D3A86.97CF894F@SteelEye.com> <16456.2775.641721.204171@notabene.cse.unsw.edu.au> <4048F9AA.1BBD67F@SteelEye.com> <406B1024.7BF88C@SteelEye.com> <16528.49083.998593.199805@cse.unsw.edu.au> <40C6273B.2060200@steeleye.com> <16590.38597.170409.499394@cse.unsw.edu.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <16590.38597.170409.499394@cse.unsw.edu.au> To: Neil Brown Cc: linux-raid@vger.kernel.org, ptb@it.uc3m.es, mingo@redhat.com, "james.bottomley" List-Id: linux-raid.ids Neil Brown wrote: > The changes to mdadm need a bit of work. > > You have added "--persistent" and "--non-persistent" flags for > --create. This is wrong. > --create always uses persistent superblocks. > --build makes arrays without persistent superblocks. Yes, I think --build didn't use to work for raid1, though, which is why I went the create route. I'll fix this. > I don't think I like --create-bitmap. A bitmap file should always be > created in the context of a particular array (partly so that the size > and uuid can be set correctly). I think I would like to bitmap to be > specified as a "--bitmap=filename" option to --create, --build, or > --grow. I haven't thought this through in great detail yet, but that > is my leaning. That all sounds fine except for --build. How do we know if we're doing the initial build or just a rebuild. We need to know this so we know whether to initialize the bitmap or simply use it. So I think we still need --create-bitmap for the build command (and then build will just use the bitmap, not initialize it). For --create I can make it so that the bitmap is always initialized using the array parameters, so no separate --create-bitmap will be needed. I'll need to work out the conflict that this will create with the --chunk option, though, since --chunk is the array chunk size for --create and --chunk is the bitmap chunk size for --bitmap-create. Any suggestions? > --examine-bitmap is a bit of a pain too. -X is usually what I use...that's a lot easier to remember and type... > I think I would like > --examine to figure out what it has been given to look at, and report > on whatever it finds. Well, that gets into a little bit of black magic when you're talking about examining a disk or partition, which could conceivably contain both an md superblock at the end and a bitmap at the front. How do we know which one it is "supposed" to be? Or do you just want examine to print information for both? That would seem a little confusing to me (granted this would only happen when a disk changed roles between bitmap and array component). -- Paul