Firstly, you need to know the expected environment before you can work out
anything.  Lets assume that you want to provide Firefox for browsing, Lotus
Notes for email, Symphony for office and x3270 for mainframe access.  All of
these run under Linux and, in addition, Notes and Symphony are Eclipse-based
which means JVM's.

What I *wouldn't* do is give each user a separate Linux guest.  I'd probably
look at around 4 Linux guests.  These guest would have all 1000 users logged
onto them.

One guest would provide the desktop.  That is, every user would log onto a
single guest using X-Windows and maybe Gnome (but I'd look at Enlightenment
as it has a lower memory footprint).  The desktop would have icons for
Notes, Symphony etc. Clicking an icon would run a remote app on one of the
other guests.  Any user running Firefox or x3270 would run the app on this
guest.

A second guest would run Notes.  Every time a user clicked the Notes icon,
it would start it would start the Notes app on the second guest.

The third and fourth guests would have Symphony workload spread between
them.  When a user clicked the Symphony icon, half would run the app on the
third guest and half on the fourth guest.

Essentially, the model is to have the basic desktop and the non-java apps on
one guest and the java workload spread over the other three guests.

I know a config along these lines would work, since the State of Florida did
something like this in the late-90's.  They were using four 8-way Intel P3
boxes running Linux with Netscape, Wordperfect and Quattro. I'm pretty sure
they were supporting more than 1000 users.

As to resources, I don't know of any benchmarks, so the following is based
on my experience with z/VM +z/Linux + Websphere.  My gut feel is that you
could probably run this sort of workload with 4 IFL's and somewhere between
96G and 128G, depending on the number of simultaneous users.  I may be
over-estimating the CPU workload.  Most of the memory requirement would be
for JVM's.  I'd allow somewhere between 128M and 256M per JVM.  So long as
the GC was running no more frequently than every 8 seconds or so and each GC
run was freeing at least 30% of the heap on each run then the sizing would
be adequate.

Another problem you are likely to hit is in networking.  The X-Windows
protocol has outbound connections from the Linux guest to the terminal.  I
don't know about your environment, but many site use VPN's internally with
each group being restricted to a single VPN sandbox.  The problem is that
many VPN clients (such as Aventail) only allow connections from the terminal
to the server, and not the other way around.

Hope this gives you food for thought

Matthew Donald

On Wed, May 13, 2009 at 7:30 AM, Ward, Mike S <mw...@ssfcu.org> wrote:

> Hello, all. I have a question. It seems that we are looking into a
> virtualized desktop environment (Single Image) on our distributed side.
> I kind of laugh at this because that's where we came from with VM and an
> OS running under VM (Green Screen) long ago and now it's making full
> circle. In VM how do you determine the amount of hardware MIPS, Disk,
> Etc... for let's say 1000 users? Is there any kind of formula to go by?
> I know in the distributed environment, it will probably take a lot of
> disk space, and as far as performance I don't think it would be as
> snappy as a real VM system. I used to work at a shop where we had 2500
> users and a few with APL, that's right APL. Anyone that's been around
> knows what APL programmers did for VM. And in that shop response time
> was good even under MVS/CICS under VM. Anyway any comments, suggestions,
> criticisms are welcome.
>
>
> Thanks.
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