Date: Tue, 4 Aug 2020 22:00:23 -0400 From: Karl Denninger <karl@denninger.net> To: freebsd-fs@freebsd.org Subject: Re: zfs scrub enable by default Message-ID: <e5e7a916-4da2-6467-1616-1b1a75f32509@denninger.net> In-Reply-To: <alpine.GSO.2.20.2008042010300.10299@scrappy.simplesystems.org> 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>
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This is a cryptographically signed message in MIME format. --------------ms090900040404050202040303 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 8/4/2020 21:21, Bob Friesenhahn wrote: > On Wed, 5 Aug 2020, Grant Gray via freebsd-fs wrote: >> >> 2. That scrubbing PREVENTS data loss. Scrubbing can only tell you=20 >> about data loss AFTER it happens. Yes, it could alert you to a=20 >> problem that prevents further data loss, but it's already too late.=20 >> Scrubbing is not a substitute for RAID, backups and proactive SMART=20 >> testing. > > Any reasonable zfs pool should have sufficient hardware redundancy to=20 > allow it sufficient time to work without losing data before a human is = > able to notice and replace the failing hardware. You assume much. Let me give you two allegedly "degenerate" cases that are actually not=20 degenerate at all. 1. A laptop or workstation.=C2=A0 It is backed up.=C2=A0 It uses ZFS beca= use it's=20 faster, and I can establish a filesystem for some project very easily=20 and quickly, it's segregated, I can work on it and destroy it trivially=20 when done.=C2=A0 I can set quotas on that, etc.=C2=A0 If I want to move i= ts=20 mountpoint, I can trivially do so. And so on.=C2=A0 Note that here there = is=20 no redundancy at all; no raidZx, no mirroring, etc.=C2=A0 I'm merely usin= g it=20 for convenience. 2. The same, but with multiple BEs.=C2=A0 Same idea, but now I can have=20 multiple OS versions and change between them for a given boot very=20 quickly while leaving my user data (and application software) alone.=C2=A0= =20 VERY useful if I'm doing code development on the OS (and I do that once=20 in a while) or application development and want to test against=20 different FreeBSD revisions (which I do a LOT.) Again, I don't get a wet = crap about redundancy, but I care very much about the convenience. My laptop is set up with ZFS and has exactly one storage device in it.=C2= =A0=20 I don't consider that foolish at all for the above reasons (and it has=20 kept me from hair-pulling exercises when drm-kmod problems bit people,=20 including me), but a scrub on an automated "schedule" basis for that=20 machine is IMHO cray-cray material. --=20 Karl Denninger karl@denninger.net <mailto:karl@denninger.net> /The Market Ticker/ /[S/MIME encrypted email preferred]/ --------------ms090900040404050202040303 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgMFADCABgkqhkiG9w0BBwEAAKCC DdgwggagMIIEiKADAgECAhMA5EiKghDOXrvfxYxjITXYDdhIMA0GCSqGSIb3DQEBCwUAMIGL MQswCQYDVQQGEwJVUzEQMA4GA1UECAwHRmxvcmlkYTESMBAGA1UEBwwJTmljZXZpbGxlMRkw FwYDVQQKDBBDdWRhIFN5c3RlbXMgTExDMRgwFgYDVQQLDA9DdWRhIFN5c3RlbXMgQ0ExITAf 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