Coda File System

CFS using DCE RPC, Directory Svcs and API Facilities

From: Jim Doyle <>
Date: Thu, 4 Dec 1997 21:53:57 -0500 (EST)
Howdy. I'm a recent new person to the list. BTW- I think this is a
phenomenal project getting Coda out there. I remember playing with a Mach Coda
laptop that a friend of mine at UMass-Amherst CS had in 1993. Great to see
this project is still moving.

I was wondering if anyone has discussed or considered the pros/cons about
hosting Coda over DCE infrastructure. Transarc has successfully unglued AFS
from Rx and LWP and got AFS 4 to use the DCE infrastructure components.
DCE has become a standard base-system component on vendor Unix (AIX, HP,
DEC Unix, avail on SGI IRIX, Solaris, ...) Coming soon for Linux and FreeBSD.

The only real advantage of using DCE as the communications layer would be
the ability to easily implement and support 'cells'. DCE cells exist outside
of DFS and provide an extremely elegant framework for accessing resources and 
objects in foreign cells. DCE includes a global directory service that works 
in conjunction with DNS to locate directory servers in foreign cells. DCE
Directory Servers are replicated for high-availability and scalability.
DCE Security, implemented on a base of Kerberos 5, provides AFS PTserver
functionality as well as the ability to create 'trust-relationships' with
foreign DCE cells. In addition, the DCE 1.2.2 code is freely available for
research and personal use.  

>From an architectural point of view, could you comment on the efficacy of
offering DCE RPC as an alternative to RPC2 in the Coda base. Are there
special semantics or facilities in RPC2 that are not available in DCE RPC
that would make this undertaking painful? DCE RPC does support the
obvious things needed:  at-most-once semantics, reliable and sequenced
communications over UDP, TCP, IDL Language with complex C types (unions,
structs, pointers, etc)

In any case, I think it would be highly to cool to offer Coda as an
alternative distributed flesystem technology in DCE in addition to
Transarc's DFS (aka AFS 4). In fact the DCE model provides a seamless
way to add a new filesystem junction to the namespace! :)

I'd jump right in on this project now if my time wasnt already spoken for.
At the present, I am porting DCE 1.2.2 to Linux and FreeBSD. Have made alot
of progress on it in the past 3 weeks, so stay tuned for announcement
of a new release snapshot, if you are a DCE user.

-- Jim

Jim Doyle                         Boston University   Information Technology
Systems Analyst/Programmer        email:   Distributed Systems
						      tel. (617)-353-8248
Received on 1997-12-04 22:02:59