Re: [Bug-ddrescue] Tip: Improving recovery chances with Seagate "F3" models

[Franc Zabkar]

At 02:07 AM 14/05/14, you wrote:

> > or it could be implemented as a small helper application. However, it 
> > requires a little knowledge of WD's Vendor Specific Commands, or access 
> > to certain commercial tools.
>
> It would be ideal if every drive came with a complete and free firmware 
> tool, but meanwhile probably the most practical solution is to manually 
> apply the fix as described in your link, and buying a drive without this 
> problem next time.

OK, let's not bother with incorporating such a feature in ddrescue. I'm now 
just asking for someone to write a small external helper application that 
prepares the drive in much the same way that a specialised hardware imager 
does.

As you are no doubt aware, cloning speed can slow down to a crawl. Some 
drives may require 1000 hours or more with ddrescue, but only 10 hours with 
a hardware tool such as DeepSpar Disk Imager. Moreover, constant thrashing 
by software tools risks accelerating the drive's total failure, either by 
killing a weak head or by corrupting a firmware module. Every time that a 
drive has difficulty with a bad sector, it adds it to the pending list. 
Such lists can grow to the point where they overflow. The drive then goes 
offline and never comes back. A subsequent reboot reports a capacity of 0MB 
and the drive is essentially inaccessible. The solution is then to clear 
the G-lists and re-lo lists, which are firmware operations.

BTW, "ROYL" drives are not limited to "recent" models. They have been 
around for 10 years, so "buying a drive without this problem" is not an 
option. EVERY WD drive exhibits this behaviour. The firmware modification 
I'm proposing involves modifying one byte and clearing the re-lo list. I'm 
not even sure that the latter is necessary. There is already an open source 
tool called idle3ctl which illustrates the nature of WD's Vendor Specific 
Commands (VSC), and I already have an open source tool to recalculate WD's 
checksums. "Manually applying the fix", as you suggest, requires some 
significant effort and knowledge, so it is far from being a "practical 
solution". In fact practical commercial tools such as PC3000 (US$10,000) 
have a single-click solution for this problem.

Ddrescue is a great tool, and I recommend it in every storage forum, but 
without an appropriate helper application it will never achieve its full 
potential. I'm disappointed that you appear to be unwilling or incapable of 
accepting and understanding its limitations.

-Franc Zabkar