From owner-freebsd-questions@freebsd.org Tue May 16 23:00:47 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 7EFF7D6EC84 for ; Tue, 16 May 2017 23:00:47 +0000 (UTC) (envelope-from drizzt321@gmail.com) Received: from mail-ua0-x236.google.com (mail-ua0-x236.google.com [IPv6:2607:f8b0:400c:c08::236]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 42435F1A for ; Tue, 16 May 2017 23:00:47 +0000 (UTC) (envelope-from drizzt321@gmail.com) Received: by mail-ua0-x236.google.com with SMTP id e55so109535402uaa.2 for ; Tue, 16 May 2017 16:00:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to; bh=MsgqpF9sbyGRbt2WcgaXZM/PUSY4l1hyeGYiycQ0KCw=; b=nzWIYgpaGVT4UtxraQaGa4CDN/M18rwIMj7/ORF7XvxppFbttDK8bTAvwjsal3YRdG jnLWCKRcnU+K+R/VzGtCXzSftUA7JRQl4eSOlp9cn3FBEk1m8rEkMe12A5YRkpIQt+zo RnZYPa3gehGW4GzxHdlrB8xB7MxMcxYs2HElOk3Xoe5Y84+uMB34ias2QmSIFeB3rs8Z 7kuIjJYclcX3P0UlcwtocTZAygR/A5VQwXA/GflKbe1PwK0pa1LSu0Jy7bvTbiaj9q8f owO17CYnjPoikFmzIIpFSiKhiM6dawRYBz5e6t1o7L7hcJlT4LBBTkO+4XCoSkprWKdp yqbQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to; bh=MsgqpF9sbyGRbt2WcgaXZM/PUSY4l1hyeGYiycQ0KCw=; b=WQGll+h7WxWkTp6aiTqmBN+3gdLRzwr1JesL12LwcSyeST8XNKSi0xw1Jx9enDRsrA ZU4DT1TD0FJpqgBtv/35ElZHyMPhPIps+XepYJwYKK6JbKAZMaQMP+OL8JdVDdlSY3j0 0fA2OTTdqvM11VsNp4ZcW8FGKrQrqR1jD2A45mq0iUYoealio5FdlJWYBCIVPVgVIC68 SF14iwjLyKbv5fN4DwEBhMHZHI5EuOnTV31vb6pPPNKiOTohowBYU9pVgvpojSX7HmDj XtPG5NU96B/RA/0XAnKX3zkdvnZ4anZlGFU/TvjGkQ0uh12V0R+F/WwrrZe9/KRVar5K E/NA== X-Gm-Message-State: AODbwcBlWhYiH0NI9jvam+rwRqS8B0nEJLiIGeKSeTpR0smkc+LdR1c2 FUSuZHJM9hM29w1IFN8SvVe2Xlz/lEEgwGI= X-Received: by 10.176.80.162 with SMTP id c31mr193433uaa.25.1494975645932; Tue, 16 May 2017 16:00:45 -0700 (PDT) MIME-Version: 1.0 Received: by 10.103.148.75 with HTTP; Tue, 16 May 2017 16:00:15 -0700 (PDT) In-Reply-To: <20170516222456.q3wuwlthgpoup7md@ozzmosis.com> References: <20170516222456.q3wuwlthgpoup7md@ozzmosis.com> From: Aaron Date: Tue, 16 May 2017 16:00:15 -0700 Message-ID: Subject: Re: ZFS root on single SSD? To: freebsd-questions@freebsd.org Content-Type: text/plain; charset="UTF-8" X-Content-Filtered-By: Mailman/MimeDel 2.1.23 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 23:00:47 -0000 --Aaron On Tue, May 16, 2017 at 3:24 PM, andrew clarke wrote: > 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. > Ah, I guess I just assumed UFS had it, I hadn't actually checked. Thanks! > > > 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 > I think most modern SSDs have pretty good checks because of how they use MLC/TLC NAND and how it fails. The biggest thing I can think of is a controller/board failure, rather than suddenly having massive number of blocks fail. However, it is a point that without copies=2 (or more) while bit-rot/corruption would be detectable, it wouldn't be possible to re-construct the bad blocks. Side note, copies=2 resiliency test ( http://jrs-s.net/2016/05/09/testing-copies-equals-n-resiliency/), rather interesting, although I probably won't be using it, at least not for an SSD. --Aaron