Really important to use ddrescue and not rsync in some cases, because rsync's temp file should be tens of gigabytes larger but isn't. Where'd that data go!? I may have realized this in the past, weeks/months ago, but just forgot:
>$ fg # 4,262,756,352 3% 13.69MB/s 2:09:14 # 2024-01-05T00:44:20.429538379Z
>rsync --archive --info=progress2 /src/100gb.file /dest/100gb.file
>[...low= 62,317,690,880 55% 5.19kB/s 2712:05:22...]
>[...high= 62,534,483,968 55% 16.99MB/s 0:48:19...]
>112,997,181,440 100% 1.30MB/s 23:02:01 (xfr#1, to-chk=0/1)
>rsync: [sender] read errors mapping "/src/100gb.file": Input/output error (5)
>134,640,936,960 119% 2.20MB/s ??:??:?? ^Z
>[1]+ Stopped [...]
>$ jobs -l
>[1]+ 25969 Stopped [...]
>$ ls -liah . # something like "kill 25969" then "ps aux | grep rsync": STAT=T for terminating?
>[...] 21G Jan 4 23:36 .100gb.file.Vcv75n
>$ mv -n .100gb.file.Vcv75n 100gb.file # 2024-01-05T06:41:39.620162833Z
>$ # so avg. = ~5 MB/s (108734425088 B/21439 sec)
Temp file=21GB, should be about 100GB. (State=T=stopped - https://askubuntu.com/questions/360252/ - kill stopped jobs via "kill -9 <PID>").