Build Your Own Virtual Cluster

By Mulyadi Santosa

July 19, 2004

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Want to build your own cluster? The first basic requirement is: You need more than one computer! But, if you only have one PC, you can use emulation software to simulate several virtual computers inside a single PC.

Emulation software simulates a complete system environment. It provides a "fake" CPU along with memory, storage, disk drives, ethernet connections and other devices. A system which is running inside the emulator is called a guest system, and the system that runs or manages the emulator and its guest systems is called the host system. In order to function, the emulator borrows resources from the host, such as CPU time for doing floating point calculations. The emulator can, in fact, drain a lot of resources.

It should be stressed that, to get acceptable speed for your virtual cluster, you have to use a fast PC. The word "fast" is relative. I built a virtual cluster on an Athlon 1800 with 256 MB RAM, a 40 GB 5400 RPM EIDE hard disk, and a GeForce2 MX 400 GPU, and I got acceptable speed for two virtual systems running simultaneously.

I used openMosix for the clustering system. OpenMosix provides Linux kernel extensions for Single System Image clustering. Many people use it because of its unique feature: automatic load balancing via process migration. Simply speaking, it allows you to spread runtime load by spreading the running task—not any kind of task, there are limitations—on all nodes based on a statistical formula carefully written and tested to make sure that overall cluster resources (CPU, memory, disk) are utilized as much as possible to yield minimal execution time of the tasks.

Normally, to experiment with openMosix, you need at least two PCs. Now, for this article, we'll combine an emulation program with openMosix to build a virtual cluster. So, the next requirement: We need a fast emulator. Popular emulators include VMWare, Bochs, Xen, Plex86, and User Mode Linux.

I used QEMU.

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