From owner-freebsd-fs@FreeBSD.ORG Thu Apr 29 16:37:40 2010 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 4279F106566C for ; Thu, 29 Apr 2010 16:37:40 +0000 (UTC) (envelope-from artemb@gmail.com) Received: from mail-pz0-f201.google.com (mail-pz0-f201.google.com [209.85.222.201]) by mx1.freebsd.org (Postfix) with ESMTP id 0E07A8FC18 for ; Thu, 29 Apr 2010 16:37:39 +0000 (UTC) Received: by pzk39 with SMTP id 39so3056283pzk.7 for ; Thu, 29 Apr 2010 09:37:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:sender:received :in-reply-to:references:date:x-google-sender-auth:message-id:subject :from:to:cc:content-type:content-transfer-encoding; bh=85gPCZJeTuNTvbDwMaHwAuwy4EK8CR2UCnP0S/jM1EQ=; b=Iz4tXHBXRyoxaMllP7iYNlO3wew84+fykTzv9izgynzlss590pO/VjlxfAYY3EKlbG 98TH5ayGoPwr2YUXcr943vOLNo64csV1+2xAMRRoOeRua13YMwAM3R6v9g+MgkO6rdV8 1thJJDaoANTtL/jVdgR/LfQ4CmwHmv6QCfjzk= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :content-transfer-encoding; b=x091mtr2aYTuF07i/S2XX4uTzkGuTG8DoLkKPLiS7f6S49Ya5G6zfjF3VB12kOW01Z TKdRrzmjVBn0JRLn5pIJsBSt8XpVEaG74BffY/SbeaNn9PPSuqHc9F4eFg1JixQnzV0h sO10uL/gQE068voWvTawx/pZ4En4fSQ4dqaHs= MIME-Version: 1.0 Received: by 10.141.14.21 with SMTP id r21mr9526228rvi.144.1272559053121; Thu, 29 Apr 2010 09:37:33 -0700 (PDT) Sender: artemb@gmail.com Received: by 10.141.29.10 with HTTP; Thu, 29 Apr 2010 09:37:32 -0700 (PDT) In-Reply-To: <4BD9B16A.10606@freebsd.org> References: <4B9FD6E0.5000303@icyb.net.ua> <4BD9B16A.10606@freebsd.org> Date: Thu, 29 Apr 2010 09:37:32 -0700 X-Google-Sender-Auth: 73091c54068b807b Message-ID: From: Artem Belevich To: Andriy Gapon Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: freebsd-fs@freebsd.org Subject: Re: few ideas for zfsloader X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 29 Apr 2010 16:37:40 -0000 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 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" >