From owner-freebsd-stable@FreeBSD.ORG Mon Oct 27 18:09:41 2014 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 74469A91 for ; Mon, 27 Oct 2014 18:09:41 +0000 (UTC) Received: from mail-ie0-x231.google.com (mail-ie0-x231.google.com [IPv6:2607:f8b0:4001:c03::231]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 3F6BBC3C for ; Mon, 27 Oct 2014 18:09:41 +0000 (UTC) Received: by mail-ie0-f177.google.com with SMTP id tp5so4885733ieb.36 for ; Mon, 27 Oct 2014 11:09:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:sender:in-reply-to:references:date:message-id:subject :from:to:cc:content-type; bh=WhsIMpGbc7ZKcpB1TXIAmEhEKlO1hAo5N92q+h4n4Ko=; b=JjRcu8Cp+mCWVzqGNCXeerpz5lfEz8Szi+mm3xftaX509W03pJE0V+ItsuJYmL1bXo odBQ05Ei/XPS87Nuyrm/BPxAZ5XH5K3wB8dEMYjwqnc7iqNL1HNtaC5D4iSdnVQNn/08 enI8O5HVJbmoA7H12ieNwx2bB6Z2gFsW/f3SneVgzvDoKiaFyzDpQjkgwkqXC1QRRCL3 iZITAE57/fiTk3GNEZfv7hTiL2zNimVoApm+B1noj3BPFn1Fv876xTGX5zJ0Dxi3IqrL LeQWlxDKbe0yqQMj6h30Dk1STuTIkaTyy9VxsmWutPau6tYWQniomQzuZ6tRjAMBm/YB KN/g== MIME-Version: 1.0 X-Received: by 10.50.128.137 with SMTP id no9mr24099194igb.0.1414433380503; Mon, 27 Oct 2014 11:09:40 -0700 (PDT) Sender: kob6558@gmail.com Received: by 10.107.11.152 with HTTP; Mon, 27 Oct 2014 11:09:40 -0700 (PDT) In-Reply-To: <6bb4cda435fb420fb663fa1d47b85a08@ultimatedns.net> References: <6978A7BF-3CB7-4088-904D-5A60D755A04C@gmail.com> <20141025113846.GY1235@albert.catwhisker.org> <6bb4cda435fb420fb663fa1d47b85a08@ultimatedns.net> Date: Mon, 27 Oct 2014 11:09:40 -0700 X-Google-Sender-Auth: 7pfDLyIOw-aTeM4qTZOFg4TVkzc Message-ID: Subject: Re: Dump time issues From: Kevin Oberman To: Chris H Content-Type: text/plain; charset=UTF-8 X-Content-Filtered-By: Mailman/MimeDel 2.1.18-1 Cc: freebsd-stable X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 27 Oct 2014 18:09:41 -0000 On Mon, Oct 27, 2014 at 9:25 AM, Chris H wrote: > On Sat, 25 Oct 2014 11:26:44 -0700 Kevin Oberman > wrote > > > On Sat, Oct 25, 2014 at 4:38 AM, David Wolfskill > > wrote: > > > > > On Sat, Oct 25, 2014 at 01:26:43PM +0200, Alban Hertroys wrote: > > > > I?m seeing something odd in my dump output that I didn?t notice > before: > > > > > > > > Dumping /root... > > > > DUMP: WARNING: should use -L when dumping live read-write > filesystems! > > > > > > (That, by the way, is pretty good advice in my experience.) > > > > > > > As long as the volume is not SU+J. Then, in my experience, it's very bad > > advice. > This reminds me of a question that I've been meaning to ask for some > time now; > Why is the FreeBSD install media using SU+J by default? > While I understand Journaling reduces retrieve times, which makes it > all seem more responsive. IMHO the consequences, and limitations it > imposes, seem to outweigh the pro's. > Just wondering... > > --Chris > > I'm aware of two issues with SU+J, one of which is annoying and the other is worse. 1. If the journal is not fully written on power fail or some other reason, you may need to do a full fsck of the volume and the behavior of the system until this is done can be very unpredictable. 2. You can't safely snapshot the system. This is what 'dump -L' does. This means that some files dumped from a live FS may not be consistent (not good!) or, if '-L' is used, the system may well hang. While I love the fast fsck times (2 or 3 seconds) after a crash, I also question the default. Still, it may be a preferred choice be used for very large file systems where a full fsck would take a very long time as long as the risks are understood. For these systems, ZFS might be a better choice. These arguments do NOT favor it being the default, IMHO. -- R. Kevin Oberman, Network Engineer, Retired E-mail: rkoberman@gmail.com