Driver retries disk errors.

[Rogier Wolff]

Hi, 

We encounter "bad" drives with quite a lot more regularity than other
people (look at the Email address). We're however, wondering why the
IDE code still retries a bad block 8 times? By the time the drive
reports "bad block" it has already tried it several times, including a
bunch of "recalibrates" etc etc. For comparison, the Scsi-disk driver
doesn't do any retrying.

So, why do we still do this?

- The driver may still work for MFM drives and less "intelligent"
  controllers?

- Someone has recently seen that this actually helps?


In fact we regularly are able to recover data from drives: we have a
userspace application that retries over and over again, and this
sometimes recovers "marginal" blocks. This could be considered "good
practise" if there is a filesystem requesting the block. On the other
hand, when this happens, the drive is usually beyond being usable for
a filesystem: if we recover one block this way, the next block will be
errorred and the filesystem "crashes" anyway. In fact this behaviour
may masquerade the first warnings that something is going wrong....

So, I'm arguing for: We remove the retry code alltogether, OR we make
an option to re-enable the retry code for MFM era drives(*) (Note: those 
are more than 10 years old, so almost (but not quite) extinct).

	Roger. 

(*) Note: Tested last month: The driver still works for MFM
drives. However, the initialization apparently is not enough
anymore. The drive did not work when the BIOS didn't think there was a
drive.

-- 
+-- Rogier Wolff -- www.harddisk-recovery.nl -- 0800 220 20 20 --
| Files foetsie, bestanden kwijt, alle data weg?!
| Blijf kalm en neem contact op met Harddisk-recovery.nl!
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/