Subject: Re: Bad sectors vs RAIDframe
To: None <,>
From: J Chapman Flack <>
List: netbsd-users
Date: 06/06/2005 11:44:51
Thor Lancelot Simon wrote:
> Most IDE drives only spare out sectors on *write* (one must ask: what,
> exactly, could they do to avoid presenting a read error on read -- and

If the question wasn't rhetorical, I think the answer is, it's a "read error"
if the drive had to apply ECC to recover the correct data; then it reassigns
the block, writes the recovered data to the new block, and returns the
recovered data to the host. It presents the read as an error only if too many
bits were off to get back by ECC, unless a different behavior was requested
in the mode page. The last drives I studied in that degree of
detail were some now decade-old Fujitsu and Seagate SCSI drives, and that was
what they did; I don't know the story for most IDE drives, but if one were
going to implement auto read reassignment I can see no reason it wouldn't be
done the same way.