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Date: Fri, 29 May 2009 08:31:54 +1000
From: Andrew Snow <andrew@modulus.org>
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To: Dmitry Marakasov <amdmi3@amdmi3.ru>
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Cc: freebsd-fs@freebsd.org
Subject: Re: ZFS scrub/selfheal not really working
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Dmitry Marakasov wrote:
>>> So, my question is why doesn't ZFS rewrite those sectors with READ
>>> errors during scrub?
>> Because of the transactional nature of ZFS it writes the fresh data in a 
>> different part of the disk and then marks the old bad sectors as free.
> Ok, then why does read errors pop up again after scrub, while they
> should have been recovered?

Because your disk subsystem is broken and keeps returning new sets of 
bad sectors.

- Andrew