Re: Cheap hardware X-terms?

[Ray Olszewski <ray@comarre.com>]

I'm one of the people on this list who have been testing the XTerminal
possibilities for Linux on old equipment.

At 11:16 AM 9/21/99 -0400, Evan Leibovitch wrote [in part]:

>I would personally wonder if old systems (ie, 486s that rarely come with
>more than 16MB of RAM) are up to the task of doing decent X service.
>Call up a single mainstream like Netscape or WordPerfect and you're
>swapping like crazy -- and I find the prospect of swapping over a
>network link to be downright chilling.

From this comment, I'm not clear, Evan, whether you understand how an
XTerminal setup works. The Netscape or WP app isn't actually running on the
486 at all ... it's running on a separate applications server, using the 486
for display only ... so the "swapping like crazy" problem you are concerned
about doesn't arise, as long as the applications server is well equipped.
Typically, you'd do something like have a dozen or more 486 XTerminals run
remote apps on a P-II/500 with 256 mB of RAM. Only the X server itself (plus
the kernel and a few support apps) actually runs on the 486, and a careful
setup can get all of this into 16 Mb easily.

I've been trying a scaled-down version of exactly this -- running the X
server on one machine to use Netscape running on another. The X server is on
an old 486/40, with either 16 or 32 mB of RAM, and I've tried it with
several different Linux distributions -- most recently Monkey Linux
(ftp://metalab.unc.edu/pub/Linux/distributions/monkey). Netscape itself in
these tests is running on a P150, 96 mB of RAM, and otherwise a light load,
and the network is a 10 mbps Ethernet, also with a light load.

This arrangement has performed beautifully, eliminating all the flakiness
I've been seeing ("heavy swapping", slow scrolling, long pauses, the
occasional actual crash) when I try to run Netscape under Linux and X
directly on a 486/40. Now I don't try to run components of the X server
itself remotely ... the entire X package itself is actually on the 486,
unlike some of the other approaches to making XTerminals that rely on NFS
mounts from a server.

From this experience, my best guess is that the critical performance issues
are the quality of the remote host that runs Netscape (or WP or whatever),
and the speed of the LAN. The report at
http://www.silvervalley.k12.ca.us/chobbs/xterms/ seems to indicate that the
remote-server issue can be handled, and I'd imagine that 100 mbps Ethernet
will suffice for the load of, say, a dozen XTerminals per application
server. For running X itself, a fairly slow 486 seems to be just fine. 

All that said, I doubt that it makes sense to use a boot PROM approach for
remote booting. This does impose on the LAN the added burden of supplying X
itself, via NFS or whatever, to each XTerminal, along with the kernel,
scratch space for logs, and the usual core Linux stuff. The alternative is
to run Linux and the XTerminal stuff locally, a setup easily accomplished
with an 80-meg hard disk, and maybe even with a 40 (on paper it should work,
but I haven't managed a working setup yet). In my experience, old 486s
typically have 100 megs or so of hard disk space, making this approach feasible.

------------------------------------"Never tell me the odds!"---
Ray Olszewski                                        -- Han Solo
Palo Alto, CA           	 	         ray@comarre.com        
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