This sort of unlimited scalability, either on multiple virtual machines or on one copy of Linux, seems to be one of the things attracting users to Linux on the mainframe. "What if you could have a system that could run the same software as PC Linux, but could scale to almost any size you needed?" asked a systems programmer at a major medical center in the Midwest, who wished not to be identified by name because the Linux mainframe project at his company is in the preliminary stages. "Instead of 10 or 50 or 100 users, what if you could support thousands in the same Linux image?"Another draw, says the Toronto Transit Commission's Webb, is ease of use. Adding another Linux server to the mainframe under VM/ESA takes about 30 minutes, he says, and circumvents the need to buy new servers, run cables between machines, or even find a place to plug in a power cord, since the server operates in a virtual environment within the mainframe. And, Webb says, "connections between Linux servers inside a mainframe can be very fast, much faster than our existing Ethernet LAN." For his part, Boyes believes that one of the largest advantages of Linux/390 lies in the underlying reliability and high availability of the S/390 hardware platform. What's more, he points out, "You don't need a multimillion dollar network monitoring and system management solution--VM includes those tools as part of the base OS, and there are dozens of excellent monitoring solutions freely available." A time and a place for Linux S/390 Computing advances do not come without challenges, however. The lack of software support will be an issue for some time and will depend solely on the skills of the systems programmers, according to Bill Stephens, a VM systems engineer at a large mainframe datacenter in Philadelphia. Drivers will need to be written for several types of devices.