The Secrets of openMosix
Richard Ferri
The ultimate promise of clusters is one of inexpensive, scalable compute
power fueled by commodity hardware. openMosix expands that promise to include
open source software. Luckily for programmers and administrators, openMosix
fulfills the promise of an open, scalable, commodity cluster solution.
For those of you who have heard of Mosix, but are wondering what openMosix
is, I'll provide a bit of background. The Mosix project, headed by Professor
Amnon Barak, began in 1977 at the Hebrew University of Jerusalem. The goal of
Mosix is to transform an unwieldy and perhaps heterogeneous pile of computers
into a single efficient cluster computing resource. This transformation is based
on a set of kernel changes, which provide a single system image cluster, and
a scheduler, which deftly moves processes to the various nodes of the cluster
based on a "least loaded" algorithm.
The Mosix project underwent a serious schism in January 2002, which spawned
a new generation of Mosix -- the openMosix project. In a dispute over the "commercial
future" of Mosix, Dr. Moshe Bar, the Mosix co-project manager since 1999, started
a new company (Qlusters, Inc.) and forked the Mosix project into the new offering,
openMosix. openMosix has quickly caught on in the clustering space, consistently
at or near the top of the most popular clustering projects list at SourceForge.
Although the long legacy of Mosix spans more than two decades, with roots
as far back as the PDP-11/45 running Bell Labs UNIX 6, and offshoots into VAX
machines and BSD UNIX, this article will only address the Linux version of openMosix
on X86 machines.
Single System Image
To fully appreciate the beauty and value of openMosix, we must understand
that big term in the opening paragraphs, the "single system image" (SSI) cluster.
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