Have you tried using partclone to create a domain logfile for ddrescue to work from? It can save a huge amount of time for a sparsely populated disk.
On Fri, Mar 20, 2026 at 2:54 PM bloup38 <[email protected]> wrote: > As I wrote in my first email to you, my goal is to recover ~140 Gb of data > stored on a 2 Tb external HDD (single partition, NTFS type) > <snip> > - I also noticed that the copy phases have orders of magnitude between > their duration: for instance, the ongoing process lasted for ~2hours (copy > pass 1 forward), then ~1h30 (copy pass 2 backwards), then 6 minutes (copy > pass 4 backwards), and currently > 6 hours for only 130Mb of the 5th > copy-pass (forward) with a remaining time displayed as 1913 days. While the > first 2 passes are expected to skip large chunks of disk in case of slow > response of the rescued disk, the subsequent two passes (3 and 4 or 4 and > 5) are described as proceeding more slowly, but with the same rule, so I > don't understand why the former last for only 6 minutes, while the second > is utterly slow. > > Le dim. 8 mars 2026 à 09:57, bloup38 <[email protected]> a écrit : > > > Dear Antonio, > > > > Thank you very much for your answer, and suggestion to use the option > '-a, > > --min-read-rate'. > > In between, I also tried to use the option -O which seemed suited, after > > noticing that the reading rate was dropping after a slow or bad area, > > without recovering unless I restart the process. Option -O apparently has > > the same effect of a manual restart, and indeed the backwards pass 2 > > finished during the night. Still a long way before the rescue ends, but > one > > step at a time. > > > > Best regards > > Bruno > > > > > > Le dim. 8 mars 2026 à 00:24, Antonio Diaz Diaz <[email protected]> a > écrit : > > > >> Dear Bruno, > >> > >> Bruno Loup wrote: > >> > First, I would like to thank you for providing ddrescue tool to the > >> community. > >> > >> You are welcome. :-) > >> > >> > I noticed some very slow regions of the disk, that I would like to > skip. > >> > I tried to use the -K (or --skip-size=) option, but it seems not to > work > >> > during backward pass: > >> > >> You need to use the option '-a, --min-read-rate' in order to skip slow > >> areas. --skip-size just sets the size to skip, but does not enable > >> skipping > >> of slow areas. You may try something like '-a 50kB'. > >> > >> > >> > http://www.gnu.org/software/ddrescue/manual/ddrescue_manual.html#g_t_002d_002dmin_002dread_002drate > >> -a > >> < > http://www.gnu.org/software/ddrescue/manual/ddrescue_manual.html#g_t_002d_002dmin_002dread_002drate-a > > > >> bytes > >> --min-read-rate=bytes > >> Minimum read rate of good non-tried areas, in bytes per second. If > >> the > >> read rate falls below this value during the first two passes of the > >> copying > >> phase, ddrescue skips ahead a variable amount depending on rate and > error > >> histories. The blocks skipped are tried in additional passes (before > >> trimming). --min-read-rate is ignored in all passes but the first two. > >> If bytes is 0 (auto), the minimum read rate is recalculated every > >> second as (average_rate / 10). > >> > >> Best regards, > >> Antonio. > >> > > >
