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ddrescue estimates 40 days to complete

Posted: Fri Jul 05, 2019 9:06 pm
by jack
Recently my 4TB external Seagate drive started having problems. It would disappear from Windows Explorer. After restarting, it'd work for a while. Eventually the drive slowed down so much that it basically hung the computer.

I've started using ddrescue to clone the drive to another Seagate 4TB drive of the same model but different revision. So far, after a day of running ddrescue, it's still on pass 1, 150,369 MB rescued, 3.75% rescued, 224 read errors, 0 bad-sector, 0 bad areas, remaining time 39d 21m. The only kind of error, and there's a lot of them, is "critical medium error, dev sdc, sector XXXXXXXXX". The sector number goes up every 500,000 - 640,000 or so. It hasn't reported any other kinds of error. Average rate is 840 kB/s. So far the errors seem to be spread out over the disk and not concentrating in clusters.

The disk is not very hot, and doesn't make much sound. The destination disk is in the computer connected with SATA cable.

Since the failing disk doesn't have any critical data on it, I'm willing to let ddrescue complete. What I'd like to know is what kind of disk failure would this indicate, and what exactly is critical medium error, sector XXX?

ddrescue estimates 40 days to complete

Posted: Sat Jul 06, 2019 6:47 am
by Jared
Given that it's a 4Tb Seagate, the odds are very high that the drive has a problem with the media cache or bad sector reallocation functions that's causing it to get stuck in a busy state. With professional tools like PC-3000 you can edit the drive's firmware to disable those functions and stabilize the drive. Unfortunately, there's no DIY method to do that.

While ddrescue is a good approach to DIY, I have serious doubts it'll complete. That issue typically gets worse and worse the more you push the drive until eventually, it stops responding at all.

If I were you, I'd carefully weigh what the data is worth before proceeding too much further. Right now, you can probably get the data recovered professionally by a company with proper tools for $500-700. But, if you push it too far DIY and the heads die, that number will go up fast. There's also the very real possibility that data could end up lost forever.

ddrescue estimates 40 days to complete

Posted: Thu Jul 11, 2019 3:16 pm
by jack
Thanks, Jared, for the information.

I'm thinking of using hddsuperclone instead of ddrescue to possibly speed up the recovery. In any case, I can afford to lose the data, so I'll continue with DIY recovery.