5.7 Is openMosix Right for You?

openMosix has a lot to recommend it. Not having to change your application code is probably the biggest advantage. As a control mechanism, it provides both transparency to the casual user and a high degree of control for the more experienced user. With precompiled kernels, setup is very straightforward and goes quickly.

There is a fair amount of communication overhead with openMosix, so it works best on high-performance networks, but that is true of any cluster. It is also more operating system-specific than most approaches to distributed computing. For a high degree of control for highly parallel code, MPI is probably a better choice. This is particularly true if latency becomes an issue. But you should not overlook the advantages of using both MPI and openMosix. At the very least, openMosix may improve performance by migrating processes to less-loaded nodes.

There are a couple of other limitations to openMosix that are almost unfair to mention since they are really outside the scope of the openMosix project. The first is the inherit granularity attached to process migration. If your calculation doesn't fork off processes, much of the advantage of openMosix is lost. The second limitation is a lack of scheduling control. Basically, openMosix deals with processes as it encounters them. It is up to the user to manage scheduling or just take what comes. Keep in mind that if you are using a scheduling program to get very tight control over your resources, openMosix may compete with your scheduler in unexpected ways.

In looking at openMosix, remember that it is a product of an ongoing and very active research project. Any description of openMosix is likely to become dated very quickly. By the time you have read this, it is likely that openMosix will have evolved beyond what has been described here. This is bad news for writers like me, but great news for users. Be sure to consult the openMosix documentation.

If you need to run a number of similar applications simultaneously and need to balance the load among a group of computers, you should consider openMosix.