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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[-- Attachment #1 --]
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
>> about data loss AFTER it happens. Yes, it could alert you to a
>> problem that prevents further data loss, but it's already too late.
>> Scrubbing is not a substitute for RAID, backups and proactive SMART
>> testing.
>
> Any reasonable zfs pool should have sufficient hardware redundancy to
> 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
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.
2. The same, but with multiple BEs. Same idea, but now I can have
multiple OS versions and change between them for a given boot very
quickly while leaving my user data (and application software) alone.
VERY useful if I'm doing code development on the OS (and I do that once
in a while) or application development and want to test against
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.
I don't consider that foolish at all for the above reasons (and it has
kept me from hair-pulling exercises when drm-kmod problems bit people,
including me), but a scrub on an automated "schedule" basis for that
machine is IMHO cray-cray material.
--
Karl Denninger
karl@denninger.net <mailto:karl@denninger.net>
/The Market Ticker/
/[S/MIME encrypted email preferred]/
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