Virtual Linux servers under z/VM: Security, performance, and administration issues

In this paper we describe our experience at Colorado State University running hundreds of virtual Linuxt servers on an IBM S/390t mainframe with the z/VMt operating system and the way we solved the security, performance, and administration problems that were encountered. With the large increase in the number of Web-based systems in the last decade, the computational requirements for supporting Web applications grew dramatically. Frequently an organization required dozens, hundreds, or even thousands of servers to support its customer load. 1,2 ''Server farms'' were created in which machines were used as Web servers, file servers, database servers, and application servers. Although not a new idea—IBM main-frames have had virtual machine capability since at least 1972 when the VM operating system (then known as VM/370) was introduced 3,4 —there has also been a recent focus on running virtual servers on powerful personal or mainframe computers. 5–9 In this paper we describe our experience at Colorado State University (CSU) running hundreds of virtual Linux** servers on an IBM S/390* mainframe 10 with the z/VM* 11 operating system. The 1980s ushered in the personal computer (PC) era, which provided us with small but powerful machines that could act as servers in the client-server model of computing. The PC came at low cost and allowed end-user control of the system, without interference from a central information technology (IT) department. As client-server computing became popular, many tasks that had been traditionally performed on mainframes were migrated to the smaller and less costly PC servers. In fact, especially with the advent in the 1990s of the freely available Linux operating system and other open-source software such as the Apache Web server, server farms consisting of dozens or hundreds of these commodity PC servers were set up to service heavily used Web sites. The ability to purchase PC servers for only a few hundred dollars drove demand away from the mainframe and to these small, inexpensive, and disposable servers. Managing large numbers of these servers, however, had its drawbacks. There had to be physical space to store them and physical wiring to interconnect Ó Copyright 2005 by International Business Machines Corporation. Copying in printed form for private use is permitted without payment of royalty provided that (1) each reproduction is done without alteration and (2) the Journal reference and IBM copyright notice are included on the first page. The title and abstract, but no other portions, of …