From owner-freebsd-fs@freebsd.org  Wed Sep 27 11:25:39 2017
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From: Borja Marcos <borjam@sarenet.es>
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Subject: Problem with the periodic scrub of ZFS pools
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Date: Wed, 27 Sep 2017 13:17:24 +0200
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Hi,

There=E2=80=99s a problem with the periodic script for ZFS pool =
scrubbing (/etc/periodic/daily/800.scrub-zfs).

It can be configured with an interval between scrubs =
(daily_scrub_zfs_default_threshold=3D=E2=80=9C17=E2=80=9D) but
the feature depends on making searches in the pool history. In a very =
active ZFS pool (Mine has
a lot of zfs dataset replications and there is a lot of zfs snapshot =
creation/deletion/replication the
scrub entries will disappear (the history has a finite length).

In my case, for example, I configured 17 days between scrubs, I actually =
get a weekly one.

A better mechanism should be used to store the timestamp of the last =
automated scrub. Custom attributes
are a good candidate, but zpool doesn=E2=80=99t have that option. What =
about adding it as a custom attribute to the
root dataset of the pool?

Ie, for a pool called =E2=80=9Ctank=E2=80=9D we could use =E2=80=9Czfs =
set freebsd_period:last_scrub=3Dtimestamp=E2=80=9D or something slmilar.

Ideas?

Thanks!




Borja.