Clarify ddrescue options
Here are some questions about ddrescue's options/parameters.
1. Please clarify what the "-t" or "--truncate" option is for. When should it be used? How does it affect the image file? Have you used it?
2. "-i" and "-s"
I know these are related, but I'm not sure how. Here's what I think. Let's say I have a 100GB drive. The following command...
sudo ddrescue -i4000M -s500M /dev/sda /media/recover/test.img /media/recover/test.log
makes ddrescue start its work 4GB from the beginning of the drive and to recover 500MB of data. Is this right? How large will 'test.img' be in this case? When should "-i" and "-s" be used?
ddrescue has had trouble with the last few drives I've worked on. I suspect the drives had problems internally. But here's what happened. ddrescue would start out at a great rate recovering data (~18MB/sec). But at the first bad spot, it would slow to a crawl (<1kb/sec) and stay there until I #1 pressed Ctrl-C, then #2 removed power from the drive. Only then would I get the "interrupted by user" message. I noticed that when ddrescue reached these spots, I would hear unusual sounds coming from the drive, as if it were stuck. I kept expecting ddrescue to just move on and make a big jump, say several gigabytes ahead, but it never did.
I'm at a loss here. What do you recommend for cases like this? The last drive I worked on, ended up dying completely due to the excessive plugging, unplugging, and re-plugging to get ddrescue to resume.
I welcome your input. Thank you!