Re: RFS vs NFS


Monkey Face@unixprt (nsc!unixprt!monkey@decwrl.dec.com)
13 Aug 87 14:39:13 GMT


In article <In article <4993@felix.UUCP>, In article <4993@felix.UUCP>, martin@felix.UUCP (Martin McKendry) writes:
> Actually, I like to think of it as RFS using volatile state, and NFS
> using permanent state (i.e., disk). In order to permit the simple
> recovery that NFS aspires to, you have to store data on disk that
> will survive a failure so that a client can do correct cache
> invalidation. This NFS does, and it completes all writes prior to
> acknowledging a write to a client. In view of these requirements,
> I feel that the term "stateless" without qualification is incorrect.
> --
> Martin S. McKendry
> {hplabs,trwrb}!felix!martin
The "stateless" term does not really refer to the 'write through'
characteristic of NFS, but to the fact that the 'server' does not
maintain 'state' related to currently opened files by 'clients'.
The client has a 'handle' for a file that can always be recognized
by the server and maintains local state as to 'offset', etc.
The server may have to 're-open' that file (if all
local users are not using it) each time a request to access that
file from a client arrives. This allows the server to go down and
come back up whilst the client can use the same 'handle' and local
state information to continue to access the file as if the server
had not gone down.
RFS on the other hand does keep state at the server and client, therefore
if the server dies, so does current 'access' to any of its files.



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