From owner-freebsd-fs@freebsd.org Wed Aug 5 04:32:40 2020 Return-Path: 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 592793A9DFC for ; Wed, 5 Aug 2020 04:32:40 +0000 (UTC) (envelope-from ryan@ixsystems.com) Received: from mail-ej1-x62d.google.com (mail-ej1-x62d.google.com [IPv6:2a00:1450:4864:20::62d]) (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 4BLzHq3yX4z4Hyl for ; Wed, 5 Aug 2020 04:32:39 +0000 (UTC) (envelope-from ryan@ixsystems.com) Received: by mail-ej1-x62d.google.com with SMTP id f24so24383263ejx.6 for ; Tue, 04 Aug 2020 21:32:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ixsystems.com; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=TsWZbdJ+H0hfG5tLHMEM9Qkp+ORrHh3aru4c11sESLo=; b=kY6rMQAhx5I6vtIWkQQgeA5nAe1aENKjTyqjVOUQ6cN/3q+FCluiV6SvfGDxqJY2i6 DMcBTkeGmxQqjWCVjDV48bZ6tZW0r2gJ4NoJ35Y4kMpz8oIziJAKQLKXJ+X5UQjTtMsO 4MK5OdqXnqMcVjsXeX3q4VlQ7aTR2A8EeyO4YyGXqMjgEIdVL1TiewcqcVLwXG9ZKycg s0IOq13JeVISDmb+xKXIDX8bOGUo064TOj/kAvK8dllOpBGCrsY5K8fLeAIUGi40RipD pXodFzbgb4g+/9A1JTa10z7Ud0V9DX5v1AlLDoRSX8F3v+2IkCAvQ6wWYPpcIoUDCR6t Ym0g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=TsWZbdJ+H0hfG5tLHMEM9Qkp+ORrHh3aru4c11sESLo=; b=gMmqbIuqpCOhZXo3sNHWx9x5hrm4DxM2B7QfUwKvm+x944L82eTlhAqZi93QGsPZkF 3hOdcjOuZDf4tExuMzb4XhOYsiQPGlhNii5YMo1TeyDDdv+NrSbHH93U1oFhfO8vbAjr pITlZpsoDGhuN50xyhtayvx8l2pyRAXHsMjodKXWJeBR1XAxhOOpFck17ms7gCFoXS79 8vFQTmQY3gIVNbtfKhEpiNkJVxW+QAmREOid6Ev/h6DQxBuIqf9h1w0SnWb1LICgwML4 3KrUSA5ijgnEJ3iW3xQM1uCacBrE96zSOV0Os2bFO01GDT7gIoVtvHyOymga96rNBXQj k6qg== X-Gm-Message-State: AOAM533rEhMPn5Y4aRjAUaxkqyvjAbfX0rxUJBCs4H0Dxfj9C2ywhaWo 1brgSMXDi9hEtCrga8hnobtP6c43mWLZvthOuykEFA== X-Google-Smtp-Source: ABdhPJyJTNRgYAbNXZs1XxBllMWngHbNh65JOa+p3LL5l4mdI2vUxXSaFLlNYor7xo/9BMyqBYDZcHh9ugJLSU94Ims= X-Received: by 2002:a17:906:82ca:: with SMTP id a10mr775198ejy.524.1596601957959; Tue, 04 Aug 2020 21:32:37 -0700 (PDT) MIME-Version: 1.0 References: <105090343.294898.1596586694925.JavaMail.zimbra@gray.id.au> In-Reply-To: From: Ryan Moeller Date: Wed, 5 Aug 2020 00:32:26 -0400 Message-ID: Subject: Re: zfs scrub enable by default To: "PK1048.COM" Cc: Grant Gray , freebsd-fs , George Wilson Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 4BLzHq3yX4z4Hyl X-Spamd-Bar: -- Authentication-Results: mx1.freebsd.org; dkim=pass header.d=ixsystems.com header.s=google header.b=kY6rMQAh; dmarc=pass (policy=none) header.from=ixsystems.com; spf=pass (mx1.freebsd.org: domain of ryan@ixsystems.com designates 2a00:1450:4864:20::62d as permitted sender) smtp.mailfrom=ryan@ixsystems.com X-Spamd-Result: default: False [-2.87 / 15.00]; ARC_NA(0.00)[]; NEURAL_HAM_MEDIUM(-0.99)[-0.991]; R_DKIM_ALLOW(-0.20)[ixsystems.com:s=google]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_THREE(0.00)[4]; R_SPF_ALLOW(-0.20)[+ip6:2a00:1450:4000::/36]; NEURAL_HAM_LONG(-1.00)[-1.004]; MIME_GOOD(-0.10)[text/plain]; PREVIOUSLY_DELIVERED(0.00)[freebsd-fs@freebsd.org]; NEURAL_SPAM_SHORT(0.13)[0.130]; TO_MATCH_ENVRCPT_SOME(0.00)[]; TO_DN_ALL(0.00)[]; DKIM_TRACE(0.00)[ixsystems.com:+]; DMARC_POLICY_ALLOW(-0.50)[ixsystems.com,none]; RCVD_IN_DNSWL_NONE(0.00)[2a00:1450:4864:20::62d:from]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:15169, ipnet:2a00:1450::/32, country:US]; RCVD_COUNT_TWO(0.00)[2]; RCVD_TLS_ALL(0.00)[] X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.33 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 05 Aug 2020 04:32:40 -0000 On Tue, Aug 4, 2020 at 11:36 PM PK1048.COM wrote: > > On Aug 4, 2020, at 8:18 PM, Grant Gray via freebsd-fs wrote: > > > 2. That scrubbing PREVENTS data loss. Scrubbing can only tell you about= data loss AFTER it happens. Yes, it could alert you to a problem that prev= ents further data loss, but it's already too late. Scrubbing is not a subst= itute for RAID, backups and proactive SMART testing. > > Scrubbing does not directly prevent data loss. Scrubbing identifies data = returned from the underlying device as corrupt or incorrect. If the zpool h= as sufficient redundancy, then no data is lost. > > But, normal ZFS operation also identifies incorrect date returned from th= e underlying device(s). > > While I have only managed a few hundred drives under ZFS, I cannot recall= one case where a proactive scrub found bad data _before_ normal operations= . Once a checksum error is reported via `zpool status` then I have found a = scrub useful to determine the extent of the drive failure. > > I know there are others with thousands of drives managed under ZFS and th= eir experience may differ. > > In terms of whether the periodic scrub should be enabled by default, I am= undecided, as I can see both sides of the argument. I would prefer to make= it a user choice during installation as one of the ZFS options (such as na= tive 4K drives, ashift=3D12 or mirrored swap). Make the default enabled, bu= t by putting it in the installation options, those who know they need it di= sabled can make sure it is off from day one and not have a rude surprise th= e first time it runs (35 days after installation). > I don't think it was mentioned on this list, but that seems to be the current direction this is heading. Providing an option in the installer, whether enabled by default or not, should address everyone's concerns. --=20 Ryan Moeller iXsystems, Inc. OS Developer Email: ryan@iXsystems.com