errors from external USB disk

[Matthias Apitz]

El día Thursday, February 27, 2014 a las 02:19:30PM -0500, kpneal at pobox.com escribió:

> > The bad block is there; if I restart the reading from 10 blocks before this
> > point, it stops at the same block:
> > 
> > # dd if=/dev/da0 of=/dev/null bs=1m skip=712860
> > dd: /dev/da0: Input/output error
> > 10+0 records in
> > 10+0 records out
> > 10485760 bytes transferred in 4.017767 secs (2609848 bytes/sec)
> 
> Bad blocks are supposed to be mapped out when rewritten.
> 
> Having said that, I used to run an external drive through a USB hub. I
> ended up with silent, random corruption. I haven't seen any corruption
> since I removed the hub, but now I don't trust USB with my data.

I have now read the entire disk with dd(1) and the bad area is only in
one are, between the are 712870 ... 712874 (based on bs=1m). I rewrote this
area with 

# dd if=/dev/zero of=/dev/da0 bs=1m oseek=712870 count=4
4+0 records in
4+0 records out
4194304 bytes transferred in 0.987089 secs (4249165 bytes/sec)

and now the area can be read fine:

# dd if=/dev/da0 of=/dev/null bs=1m skip=712869 count=10
10+0 records in
10+0 records out

I will now ree-read the entire disk with dd(1) and will overwrite 
after this entire disk from /dev/zero.

Thx

	matthias
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