Drbd is a block device which is designed to build high availability clusters. This is done by mirroring a whole block device via (a dedicated) network. You could see it as a network raid 1.
Beowulf.org is a collection of resources for the expanding universe of users and designers of Beowulf class cluster computers . These supercomputers are built on commodity hardware deploying Linux OS and open source software.
The Linux Documentation Project is working towards developing free, high quality documentation for the Linux operating system. The overall goal of the LDP is to collaborate in all of the issues of Linux documentation.