Date: Wed, 5 Aug 2020 08:15:44 -0500 (CDT) From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us> To: Karl Denninger <karl@denninger.net> Cc: freebsd-fs@freebsd.org Subject: Re: zfs scrub enable by default Message-ID: <alpine.GSO.2.20.2008050808330.10299@scrappy.simplesystems.org> In-Reply-To: <e5e7a916-4da2-6467-1616-1b1a75f32509@denninger.net> References: <cca34d1a-1892-41ec-ce45-84865100c6e1@FreeBSD.org> <CAJjvXiEXEdAFXpXkGvt4fymA17kNdp6XkZV5taGKLoP2GvMHbw@mail.gmail.com> <d1b580da-1539-5fc9-f7a3-3f013bba4ef3@FreeBSD.org> <CANCZdfq2PneFvB4rnz2iGu5srFFFjs8N=7FwRO3DYjosESWXtQ@mail.gmail.com> <CAGuotKD0mCS3KmMA-EGL1uH_fByYOhMKbPVDoTdB8dg5kC-u9g@mail.gmail.com> <105090343.294898.1596586694925.JavaMail.zimbra@gray.id.au> <alpine.GSO.2.20.2008042010300.10299@scrappy.simplesystems.org> <e5e7a916-4da2-6467-1616-1b1a75f32509@denninger.net>
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On Tue, 4 Aug 2020, Karl Denninger wrote: > Let me give you two allegedly "degenerate" cases that are actually not > degenerate at all. > > 1. A laptop or workstation. It is backed up. It uses ZFS because it's > faster, and I can establish a filesystem for some project very easily and > quickly, it's segregated, I can work on it and destroy it trivially when > done. I can set quotas on that, etc. If I want to move its mountpoint, I > can trivially do so. And so on. Note that here there is no redundancy at > all; no raidZx, no mirroring, etc. I'm merely using it for convenience. Did you remember to set copies=2 or copies=3 for zfs filesystems where you hope not to experience data loss? It needs to be set as soon as possible since it only applies to new files. This is a way to get more media redundancy, although the whole drive may fail. Zfs scrub is not going to protect your precious data from loss given just one drive unless you increase the copies setting. Zfs itself already uses redundant copies for its own data structures. Bob -- Bob Friesenhahn bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ Public Key, http://www.simplesystems.org/users/bfriesen/public-key.txt From owner-freebsd-fs@freebsd.org Wed Aug 5 13:32:43 2020 Return-Path: <owner-freebsd-fs@freebsd.org> Delivered-To: freebsd-fs@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id D3774376A81 for <freebsd-fs@mailman.nyi.freebsd.org>; Wed, 5 Aug 2020 13:32:43 +0000 (UTC) (envelope-from asomers@gmail.com) Received: from mail-oi1-f174.google.com (mail-oi1-f174.google.com [209.85.167.174]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (2048 bits) client-digest SHA256) (Client CN "smtp.gmail.com", Issuer "GTS CA 1O1" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4BMCGz0XJhz4qmy for <freebsd-fs@freebsd.org>; 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Wed, 05 Aug 2020 06:32:41 -0700 (PDT) MIME-Version: 1.0 References: <cca34d1a-1892-41ec-ce45-84865100c6e1@FreeBSD.org> <CAJjvXiEXEdAFXpXkGvt4fymA17kNdp6XkZV5taGKLoP2GvMHbw@mail.gmail.com> <d1b580da-1539-5fc9-f7a3-3f013bba4ef3@FreeBSD.org> <CANCZdfq2PneFvB4rnz2iGu5srFFFjs8N=7FwRO3DYjosESWXtQ@mail.gmail.com> <CAGuotKD0mCS3KmMA-EGL1uH_fByYOhMKbPVDoTdB8dg5kC-u9g@mail.gmail.com> <105090343.294898.1596586694925.JavaMail.zimbra@gray.id.au> <alpine.GSO.2.20.2008042010300.10299@scrappy.simplesystems.org> <e5e7a916-4da2-6467-1616-1b1a75f32509@denninger.net> <alpine.GSO.2.20.2008050808330.10299@scrappy.simplesystems.org> In-Reply-To: <alpine.GSO.2.20.2008050808330.10299@scrappy.simplesystems.org> From: Alan Somers <asomers@freebsd.org> Date: Wed, 5 Aug 2020 07:32:29 -0600 Message-ID: <CAOtMX2gO8tjp3wb-RNBcnb=zNwh5CVoF8TbLiC3SQsDcHxDf+A@mail.gmail.com> Subject: Re: zfs scrub enable by default To: Bob Friesenhahn <bfriesen@simple.dallas.tx.us> Cc: Karl Denninger <karl@denninger.net>, freebsd-fs <freebsd-fs@freebsd.org> X-Rspamd-Queue-Id: 4BMCGz0XJhz4qmy X-Spamd-Bar: - Authentication-Results: mx1.freebsd.org; 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charset="UTF-8" X-Content-Filtered-By: Mailman/MimeDel 2.1.33 X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.33 Precedence: list List-Id: Filesystems <freebsd-fs.freebsd.org> List-Unsubscribe: <https://lists.freebsd.org/mailman/options/freebsd-fs>, <mailto:freebsd-fs-request@freebsd.org?subject=unsubscribe> List-Archive: <http://lists.freebsd.org/pipermail/freebsd-fs/>; List-Post: <mailto:freebsd-fs@freebsd.org> List-Help: <mailto:freebsd-fs-request@freebsd.org?subject=help> List-Subscribe: <https://lists.freebsd.org/mailman/listinfo/freebsd-fs>, <mailto:freebsd-fs-request@freebsd.org?subject=subscribe> X-List-Received-Date: Wed, 05 Aug 2020 13:32:43 -0000 On Wed, Aug 5, 2020 at 7:15 AM Bob Friesenhahn <bfriesen@simple.dallas.tx.us> wrote: > On Tue, 4 Aug 2020, Karl Denninger wrote: > > > Let me give you two allegedly "degenerate" cases that are actually not > > degenerate at all. > > > > 1. A laptop or workstation. It is backed up. It uses ZFS because it's > > faster, and I can establish a filesystem for some project very easily > and > > quickly, it's segregated, I can work on it and destroy it trivially when > > done. I can set quotas on that, etc. If I want to move its mountpoint, > I > > can trivially do so. And so on. Note that here there is no redundancy > at > > all; no raidZx, no mirroring, etc. I'm merely using it for convenience. > > Did you remember to set copies=2 or copies=3 for zfs filesystems where > you hope not to experience data loss? It needs to be set as soon as > possible since it only applies to new files. This is a way to get > more media redundancy, although the whole drive may fail. > > Zfs scrub is not going to protect your precious data from loss given > just one drive unless you increase the copies setting. Zfs itself > already uses redundant copies for its own data structures. > -1. In my experience, based on many thousands of drives, a whole drive failure is more likely than the failure or silent corruption of a few sectors. The ZFS copies setting really isn't very useful with modern HDDs. -Alan
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