I have 2 identical USB flash devices. Each is 16 GB ext4 USB 3.0 speed. I am using them for a "backup and restore" experiment.

On one, I have a 64bit Kubuntu 14.04 install. Root is the only partition and it uses the full device. Thus, I have "sda" and "sda1".

Using QT4-FSarchiver, which is the GUI version of FSarchiver, I imaged the partition. It is about 12.10 GB.

Later I restored the imaged partition to the other ext4 formatted USB. The restore went well except for 2 problems:

1) It would not boot. I later learned that is normal because FSarchiver works at the file, not block, level.

2) The restored image was about 11.20 GB. This is 0.9 GB smaller than the original! How is that possible?

My question: Why was the restored image 0.9 GB smaller than the original?

I now realize the boot wasn't included but the missing boot could not account for the entire 0.9 GB difference. Or could it?

May not be moving some system type files. Might be using tar to make files contiguous.