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

From: Scott Dwyer
Subject: Re: [Bug-ddrescue] Tip: Improving recovery chances with Seagate "F3" models
Date: Wed, 21 May 2014 20:27:09 -0400
User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0

On 5/13/2014 12:14 AM, Franc Zabkar wrote:
The fix could be incorporated into ddrescue, 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.

If someone would be willing to write this tool, I would be only too willing to help, but only if the code were open source and freely available to all. The procedure is extremely simple and the code would be very small. In fact I could perform the required task with a small MHDD batch routine.

If I can ever find the time again to get back to my ddrutility programming for more than just bug fixes and get caught up, I may likely take up things like this. I have some really good things I was working on, but have not been able to pursue them lately.

But I think I need to work on getting a "donate" button on my site (will be working on this very soon), because when I am finally ready to release the good stuff, I think at least one item might become a bit popular. Except for Mac users... Mac users will be SOL as the good stuff only works in Linux, sorry.

Maybe I am really trying to encourage myself with this to try to make some time, but here are a few teasers:

Did you know that some newer drives have the ability to change the error timer? This is the amount of time a drive will spend when a read error is encountered, which can easily take 2-4 seconds per error. On some drives it may be able to be changed to as low as 1/10th second which can turbo charge a recovery first pass, although it does increase the number of errors when used which can somewhat offset the benefit.

Ever heard of the elusive, controversial, and now twice obsolete read long command? Ever found any freeware that can actually perform it successfully? I haven't. How would one know if it was useful or just overrated if they did not have the ability to try it for themselves?

Did you know the Linux kernel does excessive retries when read errors are encountered? As ddrescue is universal it uses normal reads so it suffers from this, although there are usually a few less retries when using the direct option. It is possible to bypass this behavior for much increased error processing performance using special pass-through commands. I am sure no one would be interested in a patch for ddrescue that would allow it to process errors 5 times faster, would they?

I have said too much...

I will not get into any conversations here about any of this, except maybe the ddrescue patch as it is directly related, but only to a point. This is Antonio's place for ddrescue and I am just responding to the post. If you wish to discuss anything else I have mentioned above, please post in the ddrutility discussion on sourceforge or email me directly.


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