I am new to data recovery software. Many have a scan step, like Recuva. I wonder if scanning a partition by data recovery software will modify the partition? I learned that never modify data on a partition if planning to recover its previous data. Thanks!
You’re wise to worry, the last thing you want to do is to write anything to a drive that you are trying to recover from.
Obviously whether a program writes to the drive or not depends on the program itself, but generally speaking, developers of data-recovery programs are aware and intelligent enough to know not to write anything to the source drive (at least not without asking the user). That’s not to say that some dummy couldn’t throw together a program and make a foolish design mistake, but if you stick to tried-and-true programs like Recuva, PhotoRec, and their ilk (anything that’s a few years old and has reviews available), you should be fine.
There’s a few things to look out for however:
Everything Synetech is true. However, there is still a risk (albeit small) that a recovery program, while scanning, could inadvertently alter a disk targeted for recovery.
This could happen due to a programming error, oversight, or even external interference/radiation. And don't forget potential issues caused by other programs or processes running concurrently or the operating system itself.
Standard practice outlines the use of a device, whenever possible, that write-blocks at the physical level to prevent inadvertent writing to the disk or media. Some exaples of physical devices include FastBloc, Tableau, and WiebeTech.
The next best alternative would be to create a physical bitwise copy of the media and run your scan/recovery on the copy and not the original.