I have been to two IBM presentations on Linux for OS/390, the excitement
within IBM and with many customers is very high.

IBM has provided four ways to run Linux under their hardware.

1) Bare Metal - One Linux system per S/390 machine
2) Lpar mode - LPAR (Logical Partition). Up to fifteen images in one
S/390 machine. Each image shares CPU's and channel (I/O) resources.
3) VM/ESA - Linux runs as a guest operating system's ) under IBM's
VM/ESA operating system.
4) Hipervisor - Stripped down version of VM/ESA.

Lets look at each one in order.

#1: I can think of better ways to use S/390 hardware.
#2: Useful for multiple operating systems per machine.
#3: This is the real sleeper here. One customer is running a web hosting
business running Linux under S/390 hardware. They run 1000 separate
Linux's under VM/ESA, and can clone a new image and give it to a new
customer in a matter of seconds. They charge half as much as everyone
else and make more profit. They did a cost analysis between S/390 and
Sun Workstations. The cost of the S/390 solution beat Sun at about 50
boxes.
#4: Look at #3.

Since about 80-90% of the worlds data is still behind S/390 hardware.
Multiple Linux's each running on S/390 hardware accessing host data at
speeds many times faster than the fastest lan has to be a win situation.

Mark Jacobs