HA clusters – Software needed for switching and failure detection
Software and hardware configurations vary according to type of cluster. High Availability clusters are used when systems need to be "always on," observes Dague. "In the real world, things break. Disks wear out. Memory goes bad. CPUs overheat."
As with other OSes, hot spare systems are required, along with HA software for detecting failures and for switching over to the backup node.
Web farm clusters – Load balancing is key
Web farm implementations come into play when extra CPU and network capacity is needed for handling large volumes of data. In this type of clustering implementation, content is distributed over multiple machines, with load balancing at the front end. Typically, Apache is used as the Web server.
Administrators can consult a couple of Web sites for Linux-based load balancing software:
Too small for clusters?
Several bootcamp attendees contended their networks are too small to benefit from Linux clusters.
However, regardless of their size, companies with HPC needs – such of those in scientific and technical fields – are seeing advantages.
In HPC solutions, many computers are tied together through a high-speed network. Applications are then rewritten into "parallelizable chunks."
"Running a simulation, for example, on one node could actually take many years," Dague maintained during the Linux bootcamp.
EOS's Bogdan says it only took his company a couple of hours to port 10 or 12 miniclusters from a homegrown Linux system to IBM's supercomputing architecture in Poughkeepsie, and to optimize the existing Melafind application for IBM's Parallel Virtual Machine (PVM).
HPC clusters – Messaging and dispatch software
Dague suggests the following open source software for HPC messaging and dispatch:
"HPC in a box"
So whether you're interested in HPC, HA, or Web farm applications, Linux clusters could hold a lot of promise for your organization. However, unless you plan to outsource the whole ball of wax, you need to get familiar with open source solutions for installation, maintenance, and specific types of clustering applications.