Re: RFS vs NFS


Guy Harris (gorodish!guy@sun.com)
16 Aug 87 09:01:10 GMT


> The price of Sun's stateless approach is that preservation of consistency
> of the file system requires that clients interrogate the server to confirm
> currency of cached entries, *whether or not those entries have changed*.

Or that you have timeouts on the cached data, which is the way SunOS does it
(and the way NFS implementations derived from the Sun implementation, which
probably includes most UNIX NFS implementations, would most likely do it).
Also, (on SunOS, at least) if you do byte-span locking on a file, the caching
on data for that file is turned off, so that it goes back to the server on
every "read".

> The main reasons we keep this data at the server are a) for cache
> invalidation, and b) to manage exclusive locking. Sun let the
> client worry about invalidation, and they don't do exclusive locking.

If by "locking" you are referring either to BSD-style file locking or
Bass/POSIX/S5-style byte-span locking, we most definitely *do* have exclusive
locking (Bass/POSIX/S5-style), we just don't do it using the NFS protocol!
There is no reason to tie all of your file-system operations to the NFS
protocol.

RFS also supports Bass/POSIX/S5-style locking.
        Guy Harris
        {ihnp4, decvax, seismo, decwrl, ...}!sun!guy
        guy@sun.com



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