[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Genera 8.1, NFS & my confusion
Date: Thu, 17 Oct 1991 14:39 PDT
From: razzell%cs.ubc.ca@Warbucks.ai.sri.com (Dan Razzell)
As a side comment on the operation of NIS, note that even if the network
were configured so that a backbone NIS server could respond to a request,
that server may be too busy to respond. It is for precisely that reason
that an NIS client is supposed to broadcast its requests, so that whatever
server is available will respond. So even when the Lispm does manage to
connect transitively, it does so by subverting a mechanism that is intended
to balance server loads.
Sorry, I couldn't let this go by without challenging it. As I
understand it, Sun NIS clients do a broadcast when they boot to get the
NIS server and then never change it unless they have a problem with the
server. Thus it is possible that even with two equally responsive
servers, all clients will wind up on one server and the load never gets
In fact, if one of the servers goes down, all its clients will likely
abandon it and never come back (until the server they go to goes down).
On our Suns right now, 36 clients are on one server and 2 clients are on
the other (one of which is the server itself). The unused server was booted
two days ago.
So much for balanced server loads.
... The filesystems, services, and network connectivity available
to one host is not transitively available to any host connected to it,
and it would be naive to think otherwise, as the Lispm guarantees to do.
Re the filesystems, call me naive. If I have access as a user on host X
and on host X I have access to file Y, then I can login to host X and
transmit that file to host Y. So why shouldn't I be able to access that
file from host Y? I grant I may have to reference it by a different
name on host Y than I did on host X and I may have to do whatever is
necessary to show that I am a valid user on host X. I've often wished
on our suns, that I could say HostX:/etc/passwd when I'm on a HostY but
instead I have to do something that is quite inconvenient. (Yes, rcp
gives some of that capability but only insofar as copying the file.
You can't easily have 3 editor buffers with the /etc/passwd file of 3
different hosts.) [I'm assuming /etc isn't exported.]
If I am allowed to change what aspects of the file system are of interest,
it could have been said:
The file name syntax, properties, and directory structures used
by one host is not necessarily the same for any other host connected to
it, and it would be naive to think otherwise, as NFS requires.
I've used my lispm to get files off Tops-20, VMS, Unix, and Mac filesystems,
plus a few more random ones that I rarely used (SAIL, ITS, ...). Our sun
users go to our MacIvory to transfer files between a Unix system and a
Mac filesystem (out on an Appletalk connection).
The Lisp Machine can't handle this kind of home directory structure, though
Unix hosts and NFS in general is quite happy with it.
And there are things that the Lispm is quite happy with that the Unix systems
can't fathom. (In any case, Barry showed you a way to fix your system.
We also do something else where /homedir/tyson = /home/dr3/tyson = ~tyson
= /tmp_mnt/home/dr3/tyson and our lispms are quite happy with it.)