Re: hardware recovery and RAID5 services

On 31/01/2022 18:59, Roger Heflin wrote:

And do not do write-sector on a disk that is in use in RAID, otherwise
that sectors data is gone.

I will completely remove a disk/partition and do --write-sectors
against it and then do a --add (don't do a re-add).    In general
though I have not had a lot of luck with the write-sector fixing
and/or forcing a reallocate even when the sector is clearly bad.  I
have to conclude (based on both WD and seagate not reallocating
sectors that reliably fail rereads in <30-seconds after just being
re-written) that pretty much everyone's disk firmware must suck.

Would --make-bad-sector work to force a reallocate?

On Mon, Jan 31, 2022 at 9:40 AM Nix [off-list ref] wrote:

quoted

On 29 Jan 2022, Wols Lists told this:

quoted

I believe there is also a way of injecting a hardware error onto a
drive. Unless you can take a backup of the backup :-) I wouldn't
recommend it at the moment, but there's some ATA command or whatever
that tells the drive to flag a sector as bad, and return a read error
until it's over-written.

See hdparm --make-bad-sector. The manpage says "EXCEPTIONALLY DANGEROUS.
DO NOT USE THIS OPTION!!". It is not lying. :)

(This is also --write-sector, which is merely VERY DANGEROUS, but can be
used to force rewrites of bad sectors. Make sure you get the sector
number right! Needless to say, if you don't, it's too late, and there's
no real way to test in advance...)

If a disk has one or more bad sectors, surely the only logical action is
to schedule it for replacement as soon as a new one can be obtained; and
if it's still in warranty, send it back.  If the data is valuable enough
to warrant use of RAID (along with, presumably, appropriate backups)
surely it is too valuable to risk continuing to use a known faulty disk?

In which case, I would suggest that dangerous experiments that try to
force the disk to reallocate the block are arguably pointless.

Just my opinion, but one that has served me well so far.

Regards,

Geoff.

-- 
Geoff Back
What if we're all just characters in someone's nightmares?