From owner-freebsd-questions@freebsd.org Tue May 16 22:25:12 2017 Return-Path: Delivered-To: freebsd-questions@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id B9874D6E2C6 for ; Tue, 16 May 2017 22:25:12 +0000 (UTC) (envelope-from mail@ozzmosis.com) Received: from hapkido.dreamhost.com (hapkido.dreamhost.com [66.33.216.122]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 947C71C00 for ; Tue, 16 May 2017 22:25:12 +0000 (UTC) (envelope-from mail@ozzmosis.com) Received: from homiemail-a56.g.dreamhost.com (sub5.mail.dreamhost.com [208.113.200.129]) by hapkido.dreamhost.com (Postfix) with ESMTP id 3C76C959CC for ; Tue, 16 May 2017 15:25:06 -0700 (PDT) Received: from homiemail-a56.g.dreamhost.com (localhost [127.0.0.1]) by homiemail-a56.g.dreamhost.com (Postfix) with ESMTP id E0C8F6003F2B; Tue, 16 May 2017 15:24:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=ozzmosis.com; h=date:from :to:cc:subject:message-id:references:mime-version:content-type :in-reply-to; s=ozzmosis.com; bh=nHbWTmCFg4TXrWW1v1wRKHy3GXg=; b= kLRziUPL6PDzyOaApO7yh3whXehsZfuwAJmdP1CPIEOOlpLV6h6vPdu/5+b0f/2h 6SpLlB4wHDUBED4koDr1k/5hpBPW11HJ6qj76roHLGQBTAvCq3vY7vy9lsbm6nUV kvnQpo4sZ8wINn/K3CnipEK8mXaPfymuwF0seZMwUYM= Received: from blizzard.ozzmosis.com (203-214-44-104.dyn.iinet.net.au [203.214.44.104]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: relay@ozzmosis.com) by homiemail-a56.g.dreamhost.com (Postfix) with ESMTPSA id 916576003F20; Tue, 16 May 2017 15:24:59 -0700 (PDT) Received: by blizzard.ozzmosis.com (Postfix, from userid 1001) id A551BB12; Wed, 17 May 2017 08:24:56 +1000 (AEST) Date: Wed, 17 May 2017 08:24:56 +1000 From: andrew clarke To: Aaron Cc: freebsd-questions@freebsd.org Subject: Re: ZFS root on single SSD? Message-ID: <20170516222456.q3wuwlthgpoup7md@ozzmosis.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170428 (1.8.2) X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 16 May 2017 22:25:12 -0000 On Mon 2017-05-15 22:45:19 UTC-0700, Aaron (drizzt321@gmail.com) wrote: > So, I've been running ZFS root mirror across 2 spinning disks, and I'm > upgrading my home server/nas and planning on running root on a spare SSD. > However, I'm unsure if it'd be better to run UFS as a single drive root > instead of ZFS, although I do love all of the ZFS features (snapshots, COW, > scrubbing, etc) and would still like to keep that for my root drive, even > if I'm not mirroring at all. I do notice that FreeBSD has TRIM support for > ZFS (see http://open-zfs.org/wiki/Features#TRIM_Support). ICYMI, FreeBSD also has TRIM support for UFS. See the -t flag for the newfs command. > So is there a good reason NOT to run ZFS root on a single drive SSD? A good question that I've often wondered about. The first reply at https://forums.freenas.org/index.php?threads/single-drive-zfs.35515/ hints at metadata corruption on a pool located entirely on a single magnetic drive possibly leading to failure of the entire pool, and given the lack of easy to use repair tools for ZFS, would require a rebuild. I think in reality this would be quite rare though, and hopefully wouldn't be a huge issue anyway provided you keep regular backups. Using an SSD might change things a little should the drive begin to fail, but I get the impression modern SSDs tend to fail a bit more gracefully than the old ones. I've no experience here and am interested in any anecdata. Keep in mind you also have other options, such as splitting the drive into separate UFS and ZFS partitions, or creating a ZFS pool from a file on UFS. The latter probably has performance drawbacks, but they might be negated by the performance of the SSD. Regards Andrew