Andrew Wiley wrote:
On Tue, Mar 24, 2009 at 8:23 PM, John Summerfield <
[email protected]> wrote:
What kind of "terminal" equipment will they be using?
Students would access their VM's through SSH.
3. What would they be doing?
Each VM will probably have a webserver hosting SVN and Trac, there will
probably be some sort of build system as well, and students will be
periodically running network server code to test stability and allow a
centralized testing location for wider scale applications.
Have you explored the use of virtual servers in Apache? It's possible to
host many websites on a single copy of a single OS on a single computer
using a single IP address.
This is true, but I'm really wanting to have students' code isolated so if a
prankster runs a forkbomb or some malicious code, everything else keeps
working. There's also more educational value in giving each project a VM;
hopefully it would at least teach basic linux shell commands. It's still
debatable whether I should have multiple webservers or one though... I'll
have to think about that.
Why is S/390 the right tool for the job?
Mostly the price, although I admit it's a poor justification. I'm also
hoping that using it would bring more stability than our current solution.
It would also (hopefully) scale better as the program grows, which is
definitely happening. We need to upgrade somehow, and this offer came at the
right time.
There's also the benefit of exposing students to the idea that mainframes
are still alive and useful (most textbooks these days cite mainframes as an
example of obselete technology that existed before PC's, unfortunately),
and, if possible, it would let me offer mainframe programming as an
independent study course.
Okay, here is what I think.
Count the cost.
Do you get a full, working system? If not, there are extra costs for the
bits that are missing.
Depending on the capabilities of your particular machine, you will have
some number of essentially discrete systems (your LPARs). I gather any
hardware reconfiguration you do involves pinching a bit off one machine
to give it to another. Whether it's enough is for you to judge.
Who is going to do the reconfiguration management?
Does this system have special power requirements? What about environmentals?
What will be the cost of transporting the system and doing the initial
installation?
What have I forgotten?
There is a case for a central server to coordinate students' work. I am
not convinced that a mainframe, even a free one, is the best tool for
the job.
For any programming students might do, it makes not a jot of difference
whether they do it on a PC running Linux or a mainframe running Linux,
the tools are the same. Since you said the students would be connecting
via ssh, I expect they already have PCs. The only Windows ssh client I
have used is putty, and while I will continue to use it, I don't like it
that well. To do the job properly, one needs Linux (or, I expect one of
the BSDs or a real Unix). If installing Linux on the student PCs'
hardware is frowned on, how about Linux inside VirtualBox (my current
favourite) or one of the MS free offerings.
This might give the students the same kind of setup so many free
software hackers have, their own PC and a central repository.
This does not preclude students from using virtual mainframes (hercules)
and checking out Linux on that.
It seems to me that, if you want the students to learn to appreciate the
benefits of a mainframe, you really need a full set of software too,
including representatives of the VM, OS and DOS families. While there
are free versions (I think I found VM on three 3330 images somewhere,
and I have MVS 3.08 around here someplace), they're pretty archaic.
If all you have is Linux running on the bare metal on a mainframe,
there's little to distinguish it favourably from a PC.
--
Cheers
John
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