Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site brl-tgr.ARPA Path: utzoo!watmath!clyde!burl!ulysses!allegra!mit-eddie!think!harvard!seismo!brl-tgr!tgr!lcc.richard@locus.ucla.edu From: lcc.richard@locus.ucla.edu (Richard Mathews) Newsgroups: net.unix-wizards Subject: Re: Extended file system on UNIX 4.2/4.3 BSD Message-ID: <1066@brl-tgr.ARPA> Date: Fri, 27-Dec-85 01:28:47 EST Article-I.D.: brl-tgr.1066 Posted: Fri Dec 27 01:28:47 1985 Date-Received: Sat, 28-Dec-85 01:47:56 EST Sender: news@brl-tgr.ARPA Lines: 62 I have one more UNIX compatible system to add to the list of those which allow for transparent remote file access. As an employee of Locus Computing Corporation, I will try to avoid making this a commercial and just stick to the facts. The LOCUS Distributed Operating System runs on a variety of cpu types (including VAX) which may all be on the network together. Differences in architectures are largely hidden from the user. In the VAX version, it is binary and source compatible with BOTH BSD 4.1 and System V Release 2. The Berkeley part of it has been enhanced with 4.2 IPC. Programs can take advantage of both the SysV features and the BSD features at the same time. A key feature is transparent access to remote files. For example, I can log in on Fafnir (which is not a VAX), but I will be in my home directory which is stored on Frodo (which IS a VAX). The name of my home directory is /u/richard. There is no indication in the name which tells you where it is stored (I don't have to say anything like /@frodo/u/richard). The file name "/u/richard" refers to the same file from anywhere on the network. This is handled by the kernel which maintains a global mount table (Fafnir knows that Frodo has a file system mounted on /u). Since it is in the kernel, programs don't have to be recompiled or relinked to use any of the LOCUS system's features. An often asked question is "where is the root directory stored?" The answer is that the root file system is usually replicated, so all sites can quickly access common programs. Any other file system can also be replicated. If a replicated file is modified, all copies will be updated automatically. If a site is down, its copy will be updated when it joins the network. A site can run without having its own copy of the root by searching the network for a site willing to act as a file server. The LOCUS system also allows for transparent access to processes on all machines. If I am on Fafnir and try to read mail with the "rdm" program, Fafnir will discover that it cannot run the program because "rdm" is compiled for a VAX. Fafnir will pick a random VAX to run it on. Pipes, signals, and terminal access will all work transparently. If all programs were such that they could only run on one machine type, that would be a problem. "rdm" is a special case of a program which has not been ported to our other machines. If you look at our /bin/csh (or most of the other programs on the root file system) you will find that it is really two files in one, so that it can run on either Fafnir or on a VAX. Running processes can also be "migrated" between machines. If I decide that the load is too high on Fafnir, I can migrate my "make" to any other machine of the same cpu type. Again, programs do not have to be recompiled or relinked to take advantage of this. I do not know when the LOCUS operating system will be publicly available. Sorry about making this so long, but I got carried away. If you care to know more, there is a book soon to be published by MIT Press which describes this system. I beleive the title is something like "The LOCUS Distributed System Architecture" and the editors are Gerald Popek and Bruce J. Walker. Richard M. Mathews Locus Computing Corporation lcc.richard@LOCUS.UCLA.EDU lcc.richard@UCLA-CS {ihnp4,trwrb}!lcc!richard {randvax,sdcrdcf,ucbvax,trwspp}!ucla-cs!lcc!richard Any opinions here are my own and do not reflect on those of my employer.