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From: SASW@MIT-MC.ARPA ("Steven A. Swernofsky")
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Subject: [LYALL: Seminar]
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Date: Sat, 7-Dec-85 13:30:56 EST
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Posted: Sat Dec  7 13:30:56 1985
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MSG:  *MSG   4790  
Date: 12/06/85 11:38:31 
From: LYALL at MIT-XX.ARPA
Re:   Seminar

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Date: Fri 6 Dec 85 11:34:59-EST
From: Neena Lyall <LYALL@MIT-XX.ARPA>
Subject: Seminar
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cc: lyall@MIT-XX.ARPA
Message-ID: <12164973450.26.LYALL@MIT-XX.ARPA>


                         Wednesday, December 11, 1985

                               2:15 Refreshments
                                 2:30 Lecture

                                Room: NE43-512A

            A DISTRIBUTED FILE SYSTEM FOR A NETWORK OF WORKSTATIONS

                       Paul Leach and Nathaniel Mishkin
                               (Apollo Computer)

The  Apollo workstation supports a distributed file system based on the concept
of a "single-level store."  Files are "objects" identified by 64 bit  IDs  that
are unique across all Apollo file systems.  A process accesses an object's data
by mapping the object into the process's address space and making normal memory
references.   The distinction between local and remote objects is known only to
the pager, which loads objects' pages on demand.

We will discuss several aspects of this architecture that we feel  are  crucial
to  its  success:    a  distributed  lock  manager,  caching  of object data, a
network-wide registry of users, and a distributed, replicated  naming  database
that is used to locate nodes based on name.

Conventional  stream  I/O  (open,  close,  read,  write,  etc.)  is provided by
"Streams."  Streams can be used to access objects in the single-level store and
other  objects  that  support  the  concept  of  stream I/O (e.g.  tape drives,
terminal) I/O lines.  Streams is object-oriented and extensible---the  behavior
of  Streams  depends  on the type of the object.  Users can define new types of
objects and write managers that implement the stream  operations  for  the  new
type.

We  will  discuss the the principles behind Streams' extensibility and describe
how we  see  it  being  used  as  the  mechanism  for  supporting  file  system
connections in a heterogeneous environment.

The   Apollo   distributed   file  system  has  been  implemented  on  a  680x0
microprocessor-based workstation.  Workstations are connected by a  12MB  token
ring;  rings  can  be  connected  by  gateways  to  form  an internetwork.  All
workstations in the internet have equal access to the distributed file  system.
The internet at Apollo Computer has over 1000 workstations.

Host: Professor Richard E. Zippel