From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Brown Subject: Re: [Patch] mdadm ignoring homehost? Date: Mon, 20 Apr 2009 15:23:52 +1000 Message-ID: <18924.1768.721791.765727@notabene.brown> References: <18899.61151.445765.360191@notabene.brown> <51C39605-BBE7-48E8-AB35-D55D0B36B3A6@redhat.com> <18919.64597.426128.498393@notabene.brown> <20090417070841.GA29681@boogie.lpds.sztaki.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: message from Gabor Gombas on Friday April 17 Sender: linux-raid-owner@vger.kernel.org To: Gabor Gombas Cc: Doug Ledford , Jon Nelson , LinuxRaid List-Id: linux-raid.ids On Friday April 17, gombasg@sztaki.hu wrote: > On Fri, Apr 17, 2009 at 01:49:41PM +1000, Neil Brown wrote: > > > As you probably know, my preferred solution is to have all arrays > > listed in /etc/mdadm.conf. If it isn't in mdadm.conf, it doesn't get > > assembled. But I don't have a lot of company in this opinion. Lots > > of people want to have arrays assembled without them being in > > mdadm.conf, and I'm trying to work with that. > > IMHO the goal to have all arrays defined in mdadm.conf would be much > better to achieve if mdadm managed that configuration itself, not unlike > how LVM metadata is handled. Of course doing that right is not exactly > easy... How does LVM manage metadata??? I assume it stored the metadata on the device. Which is what mdadm does. But as devices can move between machines..... > > > Note that 0.90 metadata does contain homehost information to some > > extent. When homehost is set, the last few bytes of the uuid is set > > from a hash of the homehost name. That makes it possible to test if a > > 0.90 array was created for 'this' host, but not to find out what host > > it was created for. So the above expedient won't work for 0.90 > > arrays, but the rest of the homehost concept (including any possible > > 'homehost=any' option) does. > > How about introducing /dev/md/by-uuid/... (or similar) and teaching > people that if they want to transparently carry their arrays from one > host to another, then they should always refer to it by UUID? This already exists, though it might be distro-dependant. /dev/disk/by-id/md-uuid-xxxxx > > Mounting file systems by UUID instead of device path got accepted by > people who really care about moving things around, so doing the same for > RAID could also work. That would be nice... NeilBrown