I have a tricky dilemma. I've got some files on two different destination drives, copied from the same source drive. The source drive had been failing, so I used dd to copy over the data to one destination (with options
conv=noerror,sync which fills error'd blocks with zero bytes) and I used ddrescue on the same source drive to copy data to a second partition, and I've heard that ddrescue also fills errors with zero bytes.
Now, I have two destination drives with near-duplicate data, except that some of the data on both of these destination drives is definitely different. I can only presume that the differences are going to be caused by those zero bytes, which seem to be located in different places amongst the data on these two destination drives. I can only presume that these differences are being caused by the parts of the files that have been zero-filled where errors had been encountered during copying. However, the zero-filled spots are different on the two separate destination drives. Most of that data consists of binary files. So some files on the source are fully intact while their counterparts on the destination are not, while other files are fully intact on the destination while their counterparts on the source are not. A lot of these files are binary files too.
Ideally, I'd like to synchronize both drives as follows:
- Compare each file, bit-by-bit.
- If the left file's bit is 1 and the right file's bit is 0, copy the 1 over to the right.
- If the left file's bit is 0 and the right file's bit is 1, copy that 1 to the left, or at least keep the 1 on the right, if two-way synchronization isn't an option.
This functionality makes sense to me, but is there a utility that can handle this automatically? I thought about using rsync for this, but it seems that rsync only checks the file based on size & timestamp or by checksum, rather than bit-by-bit, and a simple checksum won't tell you where there are 0s when there should be 1s. I also looked into rdiff and bsdiff, both of which support binary files, but both of them seem to just output a diff file, rather than doing any actual copying/synchronizing.
So is there a utility in existence that does what I'm looking for, as described in my ideal syncing behavior described above? The OS shouldn't necessarily matter, as I have access to OSX, Windows and Ubuntu.