increasing dd disk to disk transfer rate

[Christoph P. Kukulies]

On Thu, Jan 12, 2006 at 02:23:37PM -0700, Kenneth D. Merry wrote:
> > written by phk) that is designed to do disk-to-disk recovery - it
> > copys data in big slabs until it gets an error and then works around
> > the faulty area block by block.
> 
> It's called 'recoverdisk', and is in src/tools/tools/recoverdisk.
> 
> I used it to copy a friend's hard drive, and it worked well.  (Although the
> supposedly 'bad' disk didn't turn out to have any bad sectors.)
> 
> Ken

I was able to recover. The 0.99999980 copy of my damaged disk to the
identical new one, using

recoverdisk /dev/ad2 /dev/ad3

turned out to have been successful. The program was still trying to
improve the result but I didn't see any increase of recoverd block, so I
terminated it.

But the result was a fully functioning bootable (Windows XP) disk.
Probably due to the fact that the system (Windows) had been successful in
repairing itself by remapping bad clusters of files to intact areas (all
partitions were FAT32) the resulting copy was fully functional.

I never had really hard disk errors, just the frequent CHKDSK that were
required.

I believe to recall that Hitach (IBM) had a design error in their Deskstar
series when the firmware of the drive did not randomly park the head
but left it only at the beginning of the disk all the time resulting
in that area preferably being 'worn out' - I have been victim of that
bad 40 GB Deskstar series in the past several times. Don't know if this
still was the case with the Travelstar mobile computers disks series.
The frequent errors I had in hiberfil.sys point into something in that 
direction (only my little theory).

Just for the record: Before I wanted to give back in my faulty disk
to my computer supplier as a case for warranty, I zeroed out the faulty
disk.

dd if=/dev/zero of=/dev/ad2 bs=1m

It took half an hour to zero out the 80GB. Transferrate 44 MB/s?
And not a single error ? Or is this normal?

Then I tried to read back

dd if=/dev/ad2 of=/dev/zero bs=2m 

Yes, just for the fun I said 2m blocksiye. And now we come back
to FreeBSD contents:

The system froze at this command (FreeBSD 5.2.1 on that machine)


--
Chris Christoph P. U. Kukulies kuku_at_kukulies.org