Hi friends! The HDD on my laptop (running Ubuntu 20.04) started failing, so I removed and replaced with a new SSD. Most of the immediately crucial files from the HDD are backed up in multiple spots, but just for completeness I'm trying to properly back up the HDD (well, not the entire HDD but the partition with the Linux filesystem). I'm using ddrescue for this. I have the HDD connected to my laptop running Ubuntu with a SATA to USB adapter, and an external HDD with larger space that'll be where I write the recovery image.
I started with sudo ddrescue -n [input partition] [output image] [logfile], which was working fine w/ average speed 30695 kB/s. At ~8% done, however, I realised that like a dodo I forgot to unmount the HDD that I was trying to rescue (since it was auto-mounted). Of course this can cause issues in the recovery image. So I stopped the recovery process, unmounted, and restarted with the same settings above but different output image and logfile. Now, it appears to be crawling along at 479 kB/s – obviously much slower and kind of impractical.
Is there a reason this happened (logical consequence of unmounting? Somehow damaging the drive in the first run?) or is there something wrong that I can correct here?