On Tue, Apr 24, 2012 at 12:16 AM, Matt Breitbach

> So this is a point of debate that probably deserves being brought to the
> floor (probably for the umpteenth time, but indulge me).  I've heard from
> several people that I'd consider "experts" that once per year scrubbing is
> sufficient, once per quarter is _possibly_ excessive, and once a week is
> downright overkill.  Since scrub thrashes your disk, I'd like to avoid it
> if
> at all possible.
> My opinion is that it depends on the data.  If it's all data at rest, ZFS
> can't correct bit-rot if it's not read out on a regular interval.
> My biggest question on this?  How often does bit-rot occur on media that
> isn't read or written to excessively, but just spinning most of the day and
> only has 10-20GB physically read from the spindles daily?  We all know as
> data ages, it gets accessed less and less frequently.  At what point should
> you be scrubbing that "old" data every few weeks to make sure a bit or two
> hasn't flipped?
> FYI - I personally scrub once per month.  Probably overkill for my data,
> but
> I'm paranoid like that.
> -Matt
> -----Original Message-----
> How often do you normally run a scrub, before this happened?  It's
> possible they were accumulating for a while but went undetected for
> lack of read attempts to the disk.  Scrub more often!
> --
> Dan.

Personally unless the dataset is huge and you're using z3, I'd be scrubbing
once a week.  Even if it's z3, just do a window on Sunday's or something so
that you at least make it through the whole dataset at least once a month.

There's no reason NOT to scrub that I can think of other than the overhead
- which shouldn't matter if you're doing it during off hours.

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