Date: Thu, 29 Apr 2010 09:37:32 -0700 From: Artem Belevich <fbsdlist@src.cx> To: Andriy Gapon <avg@freebsd.org> Cc: freebsd-fs@freebsd.org Subject: Re: few ideas for zfsloader Message-ID: <t2jed91d4a81004290937y1799630cp85be2a6515c1f921@mail.gmail.com> In-Reply-To: <4BD9B16A.10606@freebsd.org> References: <4B9FD6E0.5000303@icyb.net.ua> <4BD9B16A.10606@freebsd.org>
next in thread | previous in thread | raw e-mail | index | archive | help
Perhaps we can hijack vdev's boot block header and/or boot block itself for these purposes. It's currently unused, according to ZFS spec. See chapters 1.3.2 and 1.4 in ZFS on-disk format: http://hub.opensolaris.org/bin/download/Community+Group+zfs/docs/ondiskform= at0822.pdf --Artem On Thu, Apr 29, 2010 at 9:18 AM, Andriy Gapon <avg@freebsd.org> wrote: > on 16/03/2010 21:07 Andriy Gapon said the following: >> 2. Currently nextboot functionality doesn't work properly with ZFS becau= se there >> is no RW support in zfsloader. =A0Adding that support seems to be quite = hard given >> the transactional nature of ZFS, checksums, compression and what not. >> Here's an alternative idea: honor nextboot.conf only if boot filesystem = has a a >> special property set on it, for example org.freebsd:nextboot. >> Then all we need is to flip the property off. >> Although doing this is still not trivial it should be simpler than files= ystem RW >> support. > > ZFS properties do, in fact, have the same nature as regular file data. > So, changing a property value (whether filesystem or pool) requires pract= ically > the same level of write support as modification of a file. > > And this seems to be quite complex to do in loader; updating all necessar= y vdevs, > doing checksums, transactions, etc. > > So, right now, I do not see a way to properly support nextboot with ZFS. > We probably should emit some warning when nextboot.conf is created on ZFS= that > there will not be automatic recovery if kernel boot fails. > > Some really weird alternative ideas: > 1. Write nextboot flag in some other place (NVRAM, special sectors of HDD= ) > 2. Use time-limited nextboot - e.g. there is a timestamp in nextboot.conf= and it > is honored until the timestamp expires. > But I won't seriously consider these. > > -- > Andriy Gapon > _______________________________________________ > freebsd-fs@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-fs > To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org" >
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?t2jed91d4a81004290937y1799630cp85be2a6515c1f921>