From: vanepp@fraser.sfu.ca (Peter Van Epp)
Newsgroups: comp.unix.large,mi.misc
Subject: Re: LISA VI paper availible via anon ftp
Date: 13 Nov 92 16:15:20 GMT
Organization: Simon Fraser University, Burnaby, B.C., Canada

rees@pisa.citi.umich.edu (Jim Rees) writes:

>In article <vanepp.721543207@sfu.ca>, vanepp@fraser.sfu.ca (Peter Van Epp) writes:

>  If I had thought of it, I knew that :-), I was expecting that you might be 
>  big enough to run out of 65000+ uids.

>It's worse than that.  There are still some Unix systems out there that
>store the uid in a signed short, which means you've only got 32,000 of them
>available.  That's roughly the size of our user community, and I think we
>have about 28,000 assigned now, even without IFS extensively deployed.  That
>doesn't leave much breathing room.

I know, we have some uids above 32k and we see some interesting problems
at times. Several of our part time operators couldn't do sudo on some
machines before we diddled sudo to use an unsigned int (which I'm suprised
worked, since the system still thinks its a signed int!), maybe we were
just lucky :-)


>  We are small enough that we could make do with
>  a single NFS fileserver to give us central file services...

>No way will that work with 30,000 users.  Client caching is absolutely
>essential, and it's also nice to have some sane kind of sharing semantics
>(unlike what NFS gives you).

While I completely agree that some form of AFS like system is the final
answer, at the time we did this (and even now for that matter) most of the
people here are not Unix experts (including me!), we had only one person that
was an experienced Unix sys admin, all the rest of us are MTS retreads (not
a bad point to be starting out from I will admit :-) ). At that time (and
probably even now) Transarc didn't support the Silicon Graphics machines,
and we already had some. 
	Since we run an Auspex file server with 6 (of the possible 8) Ethernet
ports and all the NFS service is in the machine room on secure Ethernets, we
in fact manage to support some 11,00 active users (of a total of > 20,000)
home directories from that single NFS server. We selected NFS because all
the machines we had support it (and at that point we didn't know of all the
security problems present in both NFS and Unix!). This entire phase of the
conversion was designed with the thought that it was a 2 year solution (whether
that ends up being true remains to be seen :-) ), and hoepfully when (and if!)
the time comes to move on, AFS, DFS or IFS will be a more mainstream solution
or equally possibly, we will have enough confidence in our Unix expertese to
be able to do the work required to install it for ourselves.
	The security problems we are seeing and the lack of security in NFS
(at least NFS that will work with all vendors) have caused us to restrict
access to the file server to our machines, in our machine room, where we had
hoped to be able to provide it to the desk top. 
	We are currently looking at the Novell Netware product on a Sun to 
see if we can use that to export NFS mounted home directories to Macs and PCs
in a semi secure manner (i.e. the NFS side will be controlled on a secure
ethernet on the Sun not exposing the NFS mount point to the backbone Ethernet).
	In general all parts of this conversion were probably over specified
and in most cases, selected with the capability to increase capacity by just
adding money if we found that we had under estimated the load. Both the Auspex
and the SGI machines are upgradeable to more capacity, the Auspex by adding 
more disks (which we have done) and more ethernets (which we haven't so far),
and the SGI machines by just adding more CPU boards and booting the machine.
I will note that after I commented in the the selection meeting that the
single CPU model was probably alright, after all we could just give SGI more
money and buy a another couple of cpus when it fell over dead (about 15
minutes after we turned it on), which caused the bosses to buy the 2 cpu
model right off... We in fact haven't had to upgrade yet (although with
20/20 hindsight I expect we might have had to with the single CPU model).
Should we have to, we can plug in another 2 cpu board and boot, and away
we will go, no fuss no muss, we have done it before on our previous SGI 
systems.
	I expect that this could have been done more cheaply, but no matter
what happened, we would (and still could) find uses for all the machines that
we have if we had indeed made a major under estimate of our requirements.

Peter Van Epp / Operations and Technical Support 
Simon Fraser University, Burnaby, B.C. Canada
Newsgroups: comp.unix.large,comp.org.usenix