Date: Wed, 01 Jun 2011 09:39:50 +0200 From: Arnaud Houdelette <tzim@tzim.net> To: <freebsd-stable@freebsd.org> Subject: Re: zfs-root and "safe" atomic updates Message-ID: <04039d080a0dfa9f679644e6aae42b55@tzim.net> In-Reply-To: <4DE4D2A8.7050006@FreeBSD.org> References: <63454684d7d46c2ef76cfcc979500612@tzim.net> <4DDF8E02.4060108@FreeBSD.org> <a4dc7c5cc5e907c09e1baf8dab0d2156@tzim.net> <4DE4D2A8.7050006@FreeBSD.org>
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On Tue, 31 May 2011 14:36:08 +0300, Andriy Gapon wrote: > First, strictly speaking, the loader is an executable on a > filesystem, there is no > "loader sector". If we consider the earlier boot stages, various > incarnations of > boot2 like gptzfsboot or non-MBR part of zfsboot, then it gets > interesting for > multi-disk configurations. FreeBSD has its view of disks, but BIOS > (which is used > for disk access during boot) has its own different view of disks. So > it's hard > (or impossible) to do an auto-magic thing here. One option could be > to force a > user to use its superior knowledge of a system to explicitly specify > which disk > and which boot block should be used for nextboot-ish purposes. > That, of course, would be prone to footshooting because of the human > nature. For > example, one could specify a wrong disk, boot, see that nothing > changed, realize > the mistake, specify correct disk, never clean out nextboot-ish data > on the wrong > disk, change boot order months later and get badly hurt. But it > could also be > argued that that approach would be better than nothing, which is the > case for ZFS > at the moment. > I didn't though of those footshooting scenarios, but it makes sense. I hope we'll somehow end with a proper solution. (...) > I've rebased the patch to the latest head: > http://people.freebsd.org/~avg/zfsboot.diff > >> And do you still have to change vfs.root.mountfrom once currdev set >> ? > > That should already be included into the patch. Ok. It seems the patch won't apply to 8-stable. How should I proceed to adapt it to 8-stable (if this is possible ?). Or maybe I should juste use HEAD loader ? Thanks again. Arnaud Houdelette
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