Periodic scrubbing

[Timmiej93]

Hi,

I'm new to using zfs. I've installed it and set it up, everything works great. However - after watching Linus' (LTT) video about their data loss due to bit rot, I'd like to set up periodic scrubbing. For something which I'd consider so basic it should almost be turned on by default, I'm having a very hard time really finding any information about it. None of the tutorials online about ZFS even mention scrubbing, and I can't find much with Google either. So, two questions:

Is periodic scrubbing really a good idea?
How do I enable periodic scrubbing? (Preferably not through cron)

[rincebrain]

Periodic scrubbing is an exceedingly good idea, and common advice. Debian, for example, ships with it configured to trigger one every second Sunday of the month, I believe.

Stock OpenZFS ships a systemd timer you can use to trigger it periodically, though I don't recall offhand if it enables it by default. If you're not using systemd, then cron or some init-specific cron analogue would be my suggestion.

[Timmiej93]

I noticed that too, so I did away with the .in extension. I also noticed the sbin variable, I just figured that would get taken care of. Just to be safe, I changed it to /usr/sbin.

I also had to take out the -w option on line 13. For some reason it threw an error as unrecognized, even though the option is in the documentation.

[rincebrain]

Which version are you on? It might indeed not be present.

[Timmiej93]

I just installed it very recently, so I'd assume it's the latest version:

zfs-0.8.3-1ubuntu12.13
zfs-kmod-2.0.6-1ubuntu2

[rincebrain]

You appear to be running the kernel version from one Ubuntu release with the userland from another.

Thanks, Ubuntu HWE. You're such a pal.

That would help explain why - 0.8.X doesn't have that feature, and Ubuntu doesn't ship a package with 2.0.X userland for versions that ship 0.8.X kernel modules originally, AFAIK.

My general advice for people using Ubuntu is to use jonathonf's PPA or to build it themselves.

[Timmiej93]

I understood some of those words, lol. Thanks for all the help!

[gmelikov]

You may want to look at
https://github.com/openzfs/zfs/blob/master/etc/systemd/system/zfs-scrub%40.service.in
https://github.com/openzfs/zfs/blob/master/etc/systemd/system/zfs-scrub-monthly%40.timer.in
https://github.com/openzfs/zfs/blob/master/etc/systemd/system/zfs-scrub-weekly%40.timer.in

It was added recently and will be shipped with next major stable version 2300621

[Timmiej93]

I think that worked. Output from sudo systemctl status [email protected]:

● [email protected] - Monthly zpool scrub timer for homepool
     Loaded: loaded (/etc/systemd/system/[email protected]; enabled; vendor preset: enabled)
     Active: active (waiting) since Mon 2022-02-21 16:43:12 CET; 44s ago
    Trigger: Tue 2022-03-01 00:46:55 CET; 1 weeks 0 days left
   Triggers: ● [email protected]
       Docs: man:zpool-scrub(8)

feb 21 16:43:12 Quieter2 systemd[1]: Started Monthly zpool scrub timer for homepool.

No errors, appears to be waiting, that should work right?
I assume the service is only called when the timer triggers, so it's alright if that still shows failed?

[tomchiverton]

I have zfs-2.1.12-1.fc38.x86_64 and a pool

# zfs list
NAME           USED  AVAIL     REFER  MOUNTPOINT
tank          1.26M  3.51T      104K  /tank
tank/exports    96K  3.51T       96K  /tank/exports
tank/home       96K  3.51T       96K  /tank/home

This has provided

# ls /usr/lib/systemd/system/zfs-scrub*
/usr/lib/systemd/system/[email protected]  /usr/lib/systemd/system/[email protected]
/usr/lib/systemd/system/[email protected]

but there don't seem to be running, or listed in systemctl list-timers.

Should something be happening to use these to generate ones named for each pool ?

[tomchiverton]

Edit: systemctl enable [email protected] --now works