[saurik]

I don't find that surprising at all: these are very large files, and they aren't probably not scrubbing around in them back and forth but streaming them off the disk in a single pass; so you could have 128GB of RAM and you are unlikely to get much caching on the files themselves... the only thing that matters is the directory index structures, and I wouldn't be shocked if they needed more than 16GB for that (because these are large files).