I was expecting another article about the current crop of less than POSIX filesystems, but I was pleasantly surprised to find it was about older systems with features absent in POSIX. Very interesting stuff. Kudos. I wonder if I can find some information about MTS's filesystem, which also had some neat features especially with respect to access control (PKEYs). Might be a worthwhile addition.
The whole point of the Unix FS was that the developers felt the mainframe approach (~"files are actually sorta like databases") as to complex and heavyweight.
What the OP should teach us is that there wasn't any one mainframe approach. There were many approaches, each involving many components. The process of standardizing what we now know as POSIX involved pruning a lot of unnecessary pieces, but it also inevitably involved leaving out some features that might actually have been useful. Some of them (ahem ACLs) even had to be added back in later versions of POSIX. Just as we should never stop looking for new ideas that can make our lives as programmers and users easier, we should also never forget old ideas whose time might well have come back around. It has happened too many times for the possibility to be ignored except by fools.
The MTS file system was non hierarchical, and the data model was not stream-of-bytes but rather line-numbered-record file. That said, it had some nice features, including append-only access, and program keys.
As I recall, fairly complete MTS documentation can be found at Bitsavers, and one can download a complete MTS distribution to run under emulation, see the Wikipedia article for a link.
