FYI, just a little note to let you know some real world performance results.

I use QRecall to backup my Mac, including a 25GB data file for a VMWare Fusion Virtual Machine. Today, I selected the VMWare data file in QRecall and asked it to Recapture just that file. It had been about a month since I last backed it up, and the operation took 6.5 minutes.

Then I decided to copy the VMWare data file from my Mac to the same external drive that QRecall uses. I wondered if the operation would be faster or slower (I was guessing that it would be faster to do the file copy than to use QRecall because I suspected that most of QRecall's performance comes when incrementally backing up lots of small files, and I thought it might not do so well on a single large file).

I was surprised to find that the file copy operation took 25 minutes! I was pleased that even when backing up a huge binary data file, QRecall's ability to identify the bytes that have changed and only copy them makes a huge performance impact.

Nice work!