OpenMosix - Part 1: Understanding openMosix

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As we said before, openMosix is a single system image clustering extension for the Linux kernel. It has its roots in the extremely popular MOSIX clustering project, the main difference being that it is distributed under the GNU General Public License.

It allows a cluster of computers to behave like one big multi-processor computer. For example, if you run 2 processes on a single machine, each process will only get 50% of the CPU time. However, if you run both these processes over a 2 node cluster, each process will get 100% CPU time since there are two processors available. In essence, this behavior is very similar to SMP (Symmetric Multi-Processor) systems.

Diving Deeper

What openMosix does is balance the processing load over the systems in the cluster, taking into account the speed of the systems and the load they already have. Note however, that it does not parallelize the processing. Each individual process only runs on one computer at a time.

To quote the openMosix website example :

'If your computer could convert a WAV to a MP3 in a minute, then buying another nine computers and joining them in a ten-node openMosix cluster would NOT let you convert a WAV in six seconds. However, what it would allow you to do is convert 10 WAVs simultaneously. Each one would take a minute, but since you can do lots in parallel you'd get through your CD collection much faster.'

This simultaneous processing has a lot of uses, as there are many tasks that adapt extremely well to being used on a cluster. In the later sections, we'll show you some practical and fun uses for an openMosix based GNU/Linux cluster. Next: Building An openMosix Cluster