Alexander Lesle wrote:
And what is your suggestion for scrubbing a mirror pool?
Once per month, every 2 weeks, every week.
There isn't just one answer.
For a pool with redundancy, you need to do a scrub just before the
redundancy is lost, so you can be reasonably sure the remaining data is
correct and can rebuild the redundancy.
The problem comes with knowing when this might happen. Of course, if you
are doing some planned maintenance which will reduce the pool
redundancy, then always do a scrub before that. However, in most cases,
the redundancy is lost without prior warning, and you need to do
periodic scrubs to cater for this case. I do a scrub via cron once a
week on my home system. Having almost completely filled the pool, this
was taking about 24 hours. However, now that I've replaced the disks and
done a send/recv of the data across to a new larger pool which is only
1/3rd full, that's dropped down to 2 hours.
For a pool with no redundancy, where you rely only on backups for
recovery, the scrub needs to be integrated into the backup cycle, such
that you will discover corrupt data before it has crept too far through
your backup cycle to be able to find a non corrupt version of the data.
When you have a new hardware setup, I would perform scrubs more
frequently as a further check that the hardware doesn't have any
systemic problems, until you have gained confidence in it.
--
Andrew Gabriel
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