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Re: [Bug-ddrescue] Feature Suggestion: Automatic Cooldown mode

From: Franc Zabkar
Subject: Re: [Bug-ddrescue] Feature Suggestion: Automatic Cooldown mode
Date: Sat, 01 Feb 2014 09:37:38 +1100

HDDs traverse the user area in serpentine mode. That is, they typically read between 100 to 200 tracks on one surface before switching to the next head. They then read an additional 100 to 200 tracks on this next surface before switching to the following head, and so on. AFAIK, Samsung drives typically have much larger serpentine segments, as much as 1GB or more.

You can see this behaviour in a short stroked HD Tune read benchmark graph.

How to determine number of heads using HD Tune:

The following article explains the serpentine structure.

HDD from inside: Tracks and Zones:

Here is an actual example for a WD drive:

-Franc Zabkar

At 04:31 AM 1/02/14, you wrote:
Hello David.

David Deutsch wrote:
The curious thing (well, to me at least, you guys might've seen it all
before) is that there seems to be a pattern to the bad sectors. Here
is a screenshot of ddrescueview:

Nice image. Maybe ddrescue could trim drives like this more efficiently, or even try to predict the size of the next bad area. Ddrescue tends to become more intelligent after every interesting report sent to this list. :-)

Could you send me the (compressed) logfile? I'll try to improve the trimming algorithm with it. Thanks.

So - if somebody knows anything I can do to speed this up, I would be
very greatful for suggestions!

The size of each error seems to be large (about 10MB), so the '--try-again' option may read all those non-trimmed blocks fast.

Good luck and best regards,

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