From owner-freebsd-stable@FreeBSD.ORG Sun Mar 23 19:09:06 2014 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 7FC44B62 for ; Sun, 23 Mar 2014 19:09:06 +0000 (UTC) Received: from mail.koukaam.se (mail.koukaam.se [193.86.201.130]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id 1288CA97 for ; Sun, 23 Mar 2014 19:09:05 +0000 (UTC) Received: from [192.168.1.39] (unassigned-81-90-254-125.ujezd.net [81.90.254.125] (may be forged)) (authenticated bits=0) by mail.koukaam.se (8.14.5/8.14.5) with ESMTP id s2NJ8mBO041598 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NO); Sun, 23 Mar 2014 20:08:53 +0100 (CET) (envelope-from knezour@weboutsourcing.cz) Message-ID: <532F313B.5040809@weboutsourcing.cz> Date: Sun, 23 Mar 2014 20:08:43 +0100 From: Ondra Knezour User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: Karl Denninger , freebsd-stable@freebsd.org Subject: Re: ZFS cautions (pool flag additions committed) References: <532F1ED8.8010004@denninger.net> In-Reply-To: <532F1ED8.8010004@denninger.net> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.17 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 23 Mar 2014 19:09:06 -0000 Dne 23.3.2014 18:50, Karl Denninger napsal(a): > When ZFS code imports are brought forward that add feature flags there > is a potential time bomb for existing users in that creation of a new > pool becomes non-revertible (except read-only!) with regard to mounting > on older revisions of the code. > > The same thing happens if you do a "zpool upgrade" of course, but at > least that's an explicit act. You might not realize that you're at risk > on a pool create, however, unless you **carefully** scrutinize the flags > that were on the last version compared against the current one. > > The primary "gotcha" here occurs if you don't upgrade your emergency > boot media and for some reason you need to boot from a CD or USB key -- > you can be left SEVERELY screwed, and since -RELEASE is typically not > rebuilt when this happens if you don't have a second machine laying > around on which you can build a RELEASE image.... > > I've caught this twice now since 10.0-RELEASE shipped and, while I > haven't been bit by it, it serves as a caution because eventually > someone tracking -STABLE is going to get badly hurt and be left with an > unrepairable system. IMHO there should be some sort of notice on the > list when new zpool feature flags show up so you're fairly warned that > building a new emergency boot media copy is required if you intend to > track -STABLE on a continuing basis. > Excellent candidate for the /usr/src/UPDATING file? -- Ondra Knezour