The POSIX file system

[Moderator, John Quarterman]

From: jbs at eddie.mit.edu (Jeff Siegal)
Date: Mon, 3 Nov 86 17:44:44 EST
Organization: MIT, EE/CS Computer Facilities, Cambridge, MA

In article <6206 at ut-sally.UUCP> guy at sub.com (Guy Harris)
>[...]  The file system was implemented by a process that ran in supervisor
>mode and which received messages telling it to do things like read from or
>write to a file.  Other operating systems, like RSX-11 and VMS, did the same
>thing.  I believe the latest descendents of MERT, and VMS, have moved the
>file system back into the kernel for performance reasons.

Quite far off, actually (at least in the case of VMS).  Current
versions of VMS have replaced the disk filesystem ACP (which
previously was a separate process) with the XQP, a separate instance
of which exists in _each_process_ (the code is shared).  This resulted
in some significant performance _improvements_, and a filesystem which
extends fairly easily and quite completely (including record/file
locking, etc.) over different machines (using DEC's inter-system CI
bus).

Jeff Siegal

Volume-Number: Volume 8, Number 31