Sector size in and out suggestion and question

[Lucian Maly]

Hi GNU ddrescue,

I would like to make a suggestion to add another option of sector
(hardware block) size of output device and differentiate it from
already existing --sector-size for input device - e.g.:
--sector-size-in=bytes
--sector-size-out=bytes

The problem i encountered is the following:
I was restoring from old USB disk /dev/sdb (3TB, logical sector size
4096) to new USB disk /dev/sdc (4TB, logical sector size 512):

Disk /dev/sdb: 2.7 TiB, 3000558944256 bytes, 732558336 sectors
Units: sectors of 1 * 4096 = 4096 bytes
Sector size (logical/physical): 4096 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0x000246c6
Device     Boot Start       End   Sectors  Size Id Type
/dev/sdb1         256 732558335 732558080  2.7T  7 HPFS/NTFS/exFAT

Disk /dev/sdc: 3.7 TiB, 4000752599040 bytes, 7813969920 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0x000246c6

I omitted --sector-size as it defaults to 512 thinking it matches the
/dev/sdc sector size. I did run the following two commands, which took
two days:

sudo ddrescue -n /dev/sdb /dev/sdc --force rescue.map
GNU ddrescue 1.25
Press Ctrl-C to interrupt
     ipos:  584810 MB, non-trimmed:        0 B,  current rate:   15018 B/s
     opos:  584810 MB, non-scraped:    1764 kB,  average rate:  23639 kB/s
non-tried:        0 B,  bad-sector:    25600 B,    error rate:     170 B/s
  rescued:    3000 GB,   bad areas:       50,        run time:  1d 11h 15m
pct rescued:   99.99%, read errors:      103,  remaining time:          3m
                              time since last successful read:          0s
Finished

sudo ddrescue -r3 /dev/sdb /dev/sdc --force rescue.map
GNU ddrescue 1.25
Press Ctrl-C to interrupt
Initial status (read from mapfile)
rescued: 3000 GB, tried: 1789 kB, bad-sector: 25600 B, bad areas: 50
Current status
     ipos:  584810 MB, non-trimmed:        0 B,  current rate:       0 B/s
     opos:  584810 MB, non-scraped:        0 B,  average rate:       0 B/s
non-tried:        0 B,  bad-sector:    1781 kB,    error rate:     256 B/s
  rescued:    3000 GB,   bad areas:       27,        run time:  9h 31m 57s
pct rescued:   99.99%, read errors:    13870,  remaining time:         n/a
                              time since last successful read:  7h 14m 34s
Finished

However even though ddrescue reported it rescued 3TB, I only ended up
with partition that is reported 8x times smaller (4096/512=8):
Disk /dev/sdc: 3.7 TiB, 4000752599040 bytes, 7813969920 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0x000246c6
Device     Boot Start       End   Sectors   Size Id Type
/dev/sdc1         256 732558335 732558080 349.3G  7 HPFS/NTFS/exFAT

Question1: Is there any way to fix that now without running it again?
I'm afraid the disk will not handle another ~48hrs run.
Question2: How do you currently specify destination sector size? It
does not seem to be possible - no mentioning of that in your manual.

Many thanks for your great work,

--
LUCIAN MALY, RHCA
SENIOR CONSULTANT, CUSTOMER SOLUTIONS GROUP
Red Hat Asia-Pacific Pty Ltd | people.redhat.com/lmaly