questions about File System Switch

[Guy Harris]

>BSD uses the VFS which is more more well suited for adding new FS
>types.

Err, umm, no, it doesn't.  BSD has only one file system type, and no
switch.

SunOS was the first UNIX OS to include the VFS mechanism; other systems
have adopted it as well as part of picking up NFS (although S5R3-based
systems may have shoehorned it into the FSS).

One UNIX release that will be adopting VFS will be System V Release 4.0.

>The buffer cache routines are part of the BSD VFS.

The advantage of the BSD buffer cache routines (which are, obviously,
not part of the BSD VFS since BSD doesn't have a VFS) is that they're
not tied to a particular block size; this is because the 4.2BSD file
system supports multiple block sizes, and has to deal both with blocks
and frags.