[Bug-ddrescue] Feature Suggestion: Automatic Cooldown mode

[David Deutsch]

Hey everybody,

I have this failing WD Green Line 2TB drive (SMART counts errors in
the five figures, tons of bad sectors right through tons of family
photos that I did not have backed up, like an idiot...) that I'm
currently trying to rescue and I've come across a possibly interesting
problem.

I'm making a full disk-to-disk copy using the following command:

sudo ddrescue -f -n -d /dev/sdf /dev/sde logfile

(ddrescue v. 1.16, copying to another 2TB drive)

With that, I'm getting quite good speed rates considering the state of
the disk - around 50-100MB/s (never much faster than that, though):

Current status
rescued:    25877 MB,  errsize:   6442 MB,  current rate:   92667 kB/s
   ipos:    32319 MB,   errors:      94,    average rate:   44372 kB/s
   opos:    32319 MB,     time since last successful read:       0 s
Copying non-tried blocks...

However, every time an error is found and ddrescue has worked through
it (which can take up to a minute):

Current status
rescued:    26322 MB,  errsize:   6576 MB,  current rate:        0 B/s
   ipos:    32898 MB,   errors:      95,    average rate:   11393 kB/s
   opos:    32898 MB,     time since last successful read:      53 s
Copying non-tried blocks...

...the speed drops to around just a few kB/s and stays there:

Current status
rescued:    26324 MB,  errsize:   6710 MB,  current rate:     6144 B/s
   ipos:    33034 MB,   errors:      95,    average rate:    7615 kB/s
   opos:    33034 MB,     time since last successful read:       0 s
Copying non-tried blocks...

Unless I restart it! So I ctrl+c and wait for a bit, restart the
command and it shoots up to 100MB/s again:

Current status
rescued:    26555 MB,  errsize:   6710 MB,  current rate:   92798 kB/s
   ipos:    33265 MB,   errors:      95,    average rate:   38464 kB/s
   opos:    33265 MB,     time since last successful read:       0 s
Copying non-tried blocks...

Actually, If I wait a seemingly fixed period of time (I have figured
out around 20-30 seconds), I get pretty consistent rates that way. I'm
now chomping at the drive at about 1GB intervals.

I made an earlier attempt where I just let ddrescue run and after
three days, it was still stuck idling between 32kb and 64kb. At 2TB,
that would put the time to rescue the full drive in the hundreds of
days - clearly not a workable solution. I had barely managed to get
20GB out of the drive, while, as you see from the examples above, I'm
now at 30+GB after just about 4 hours or so.

---

It would appear to me that this is hardware related. Possibly the
drive simply can't take long copying cycles anymore or is heating up
slightly (although I have it very well ventilated) in the process and
doesn't like that.

Maybe there is already a feature for that which I'm missing, but I
think a "let the drive cool down for X seconds after you've found an
error" could be a neat addition. It would at least save me a lot of
manual work ;-)

Among the other things that I have tried were changing the sector
size, but I started ddrescue with it set to 256k (I think) and it
instantly claimed that it was finished (wasn't sure how to recover
from that). Also, using -d seems to have improved my speed in general
and for a while I also tried -D, but I'm not sure that did anything
(that one is only about the drive you copy /to/, right?).

---

If anybody has any tips or suggestions, I'd be more than happy to hear
about them! As I would be to supply more information about this case
if need be, of course.

Oh, and - I'm following the 'Example 1' from the manual here, planning on using

ddrescue -d -f -r3 /dev/sdf /dev/sde logfile

for the second pass.

cheers and thanks already,
David