recoverdisk strategy

[Christoph P.U. Kukulies]

Presently I'm again in the situation to have to recover a hard disk that 
has a Windows NTFS on it, refused to
boot Windows 7 and has a lot of I/O-Errors.

I connected the disk to my FreeBSD system and now I'm trying to create a 
dump of it using "recoverdisk".

But it gives I/O-errors lots and lots and this quite slowly:


(ada2:ahcich0:0:0:0): CAM status: ATA Status Error
(ada2:ahcich0:0:0:0): ATA status: 00 ()
(ada2:ahcich0:0:0:0): RES: 00 00 00 00 00 00 00 00 00 00 00
(ada2:ahcich0:0:0:0): Error 5, Retries exhausted
(ada2:ahcich0:0:0:0): FLUSHCACHE48. ACB: ea 00 00 00 00 40 00 00 00 00 00 00
(ada2:ahcich0:0:0:0): CAM status: ATA Status Error
(ada2:ahcich0:0:0:0): ATA status: 71 (DRDY DF SERV ERR), error: 04 (ABRT )
(ada2:ahcich0:0:0:0): RES: 71 04 9d 00 32 40 00 00 00 04 00
(ada2:ahcich0:0:0:0): Retrying command
(ada2:ahcich0:0:0:0): FLUSHCACHE48. ACB: ea 00 00 00 00 40 00 00 00 00 00 00
(ada2:ahcich0:0:0:0): CAM status: ATA Status Error
(ada2:ahcich0:0:0:0): ATA status: 71 (DRDY DF SERV ERR), error: 04 (ABRT )
(ada2:ahcich0:0:0:0): RES: 71 04 9d 00 32 40 00 00 00 04 00
(ada2:ahcich0:0:0:0): Error 5, Retries exhausted
(ada2:ahcich0:0:0:0): Synchronize cache failed

Setting
sysctl kern.cam.ada.retry_count=0

seems to run faster but still it's not gathering any percentage. Still 
staying at 0.00000 after running some 10 minutes or so.

What else could I do? Skipping disk blocks/cylinders?

The aim is to produces an image of the disk that contains as much as 
possible sane sectors with the rest filled wth 0,
so that the dump still keeps a mirror of the disk (with holes in it, of 
course). Once being done, I'd apply a

program like "testdisk" that can do a deep search and can try to recover 
the partition information and the file system (hopefully).


--

Christoph