I'm using rsync to copy all files from one 3TB external disk formatted HFS+ to another 3TB external disk formatted exFAT.
I've double checked both disks are exactly the same size and formatted the destination disk right before I began the copy, and in fact the source disk has 38GB space, so there's about 2962 GB of files (1TB = 1000GB on my system).
Rsync has failed around 90% of the way through having filled up the destination disk. Can this be explained by differences between HFS+ and exFAT? Is exFAT much more wasteful of disk space when storing files compared to HFS+?