[ih] Distributed file systems [was: As Flag Day approaches at CMU]

[Brian E Carpenter]

I've never looked into the early history of distributed file systems. Was that work at MIT ever published? Was it pioneering or did someone else do it first?

My favourite paper in that area is the "Unix United" paper [1] from 1982.

[1] https://doi.org/10.1002/spe.4380121206 (paywalled) or
http://homepages.cs.ncl.ac.uk/brian.randell/Papers-Articles/399.pdf
Regards/Ngā mihi
    Brian Carpenter

On 07-Sep-25 08:04, Guy Almes via Internet-history wrote:
> Jack,
>     Thanks very much.
>     So this was in place by the mid-70s, right?
> 	-- Guy
> 
> On 9/6/25 3:15 PM, Jack Haverty via Internet-history wrote:
>> ITS at MIT circa early 1970s used a naming convention for files --
>> <device>:<directory>;<name1> <name2>   So, for example, I logged in to
>> MIT-DM as JFH.  My files on disk were things like DSK:JFH;THESIS TJ6
>> File names were limited to alphanumerics of 6 characters or less
>> (motivated by what you could encode into a 36-bit PDP-10 memory location).
>>
>> Once the ARPANET and NCPs appeared, the 'net was a new toy, so people of
>> course experimented with how to use it.  I don't remember the details or
>> timing (sometime in early 1970s), but at but at some point the Message
>> Of The Day announced a new capability - you could use files on some
>> other ITS machine just by using a different <device> to specify the DSK
>> on some other ITS machine.
>>
>> So, for example, from the MIT-AI machine a user could get to my file on
>> the DM machine by specifying DM:JFH;THESIS TJ6.
>>
>> Similarly, from my account on MIT-DM, I could get to another machine's
>> files by using a name such as AI:TK;NEWS ITS to get at Tom Knight's file
>> on the AI machine.
>>
>> This provided more flexibility than FTP.  You could use a remote file in
>> any program that knew how to use files on devices.  To the program, the
>> remote disk looked and behaved like a local disk. (More or less -
>> problems of "global LANs" were still be be surfaced)
>>
>> I don't recall at all how this worked, or who implemented it.  IIRC, it
>> took advantage of an interprocess communication capability called the
>> "JOB/BOJ device", which enabled one program to open a JOB device, and
>> another program to open the corresponding BOJ (JOB reversed) device, and
>> send whatever they liked back and forth.  But I don't remember details.
>>
>> We also had the ability for one process (aka "job") to map some or all
>> of another process' address space into its own address space.  I can't
>> recall if anyone got motivated to get that working across the ARPANET
>> though.   If so, it would probably have been done using the same
>> internal mechanisms that got the remote file systems capability.
>>
>> However, for anyone curious, the ancient ITS system is online and has
>> even been resurrected so you can look at the code or even run it on your
>> modern computer - see https://github.com/PDP-10/its
>>
>> Jack Haverty (JFH at MIT-DM in the 70s)
>>
>> On 9/6/25 09:28, Guy Almes via Internet-history wrote:
>>> Noel,
>>>    So this was a real networked file system (and not just lots of FTP)?
>>>    Very interesting,
>>>      -- Guy
>>>
>>> On 9/6/25 11:35 AM, Noel Chiappa via Internet-history wrote:
>>>>
>>>>       > From: Guy Almes
>>>>
>>>>       > There are probably a number of ARPAnet sites where the ARPAnet
>>>>       > served this LAN role in the pre-Ethernet days.
>>>>
>>>> Notably MIT, where the 4 ITS machines shared their file systems over the
>>>> ARPANET.
>>>>
>>>>      Noel
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