Re: forcing a read on a known bad block

[Patrik Jonsson <patrik@ucolick.org>]

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hi dean,

dean gaudet wrote:
> 
> the other disk was in a raid5 ... 5 disk raid5, so 20% chance of the bad 
> block being in parity.  i copied the kernel code to be sure, and sure 
> enough the bad block was in parity... just bad luck :)  so i can't force a 
> read there any way that i know of...

well, for raid5 you can use 'echo repair > /sys/block/mdx/md/sync_action'

This does a 'simulated reconstruction' and has triggered this for me in
the past. (For some reason 'check' instead of 'repair' did not, even
though it should have tried to read all the blocks then, too...)

That said, I have one disk in an 8-disk raid5 that says 'current pending
sector 1', and another that says 'offline uncorrectable 1', and they
have been doing so for months. Neither SMART extended tests or full
raid5 resyncs have either failed or fixed this, so I don't know what's
up with that...

cheers,

/Patrik

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