Note Bruce has retired since he wrote the following, but the 
paper describing the work is:   
Open Single System Image (openSSI) Linux Cluster Project, Bruce J. Walker, Hewlett-Packard

Bruce.walker@hp.com

Abstract

The openSSI Cluster project is an ongoing open source project which was started two years ago to bring together some of the best Linux and Unix clustering technologies into a single integrated and yet modular project.

Linux is rich in cluster technology but is segmented into 6 different cluster areas
- high performance, load-leveling, web-service, storage, database and high availability. The openSSI project address all cluster environments by simultaneously addressing the three key cluster goals - availability, scalability and manageability.

To accomplish this ambitious goal, the project was started with a Linux adaptation of the NonStop Clusters for Unixware code, contributed by Compaq/HP. That code included membership, internode communication, clusterwide process management, clusterwide devices, a cluster filesystem, clusterwide IPC (pipes, fifos, msgqueues, semaphores, etc.) and clusterwide tcp/ip networking. Other open source clustering code has been integrated into the modular architecture, including openGFS, openDLM, LVS, Lustre and a small component of Mosix. The architecture of the project allows for subsetting and substitution of components. A full function initial release is available in both source and RPM form. Many enhancement opportunities still exist both in integrating with other technologies and by improving scalability and availability.