I've considered this question and reviewed the folder structure on the CS where documents are stored. I There is a complex folder structure setup by the system but ultimately there is a folder setup with same number as the physical document ID. Within that 2 documents are stored, a metadata file and the original (compressed).
I'm not certain how the system locates this set of files in a efficient manner but can confirm perform to be acceptable and comparable to MaxDB based CS.
FileSystemStorage have advance of backup and restore and provides a easy means of data management we like.
Hope this helps some.