IScale

So, what is Ganglia in details?
Quoted from ganglia official site:

Ganglia is a scalable distributed monitoring system for high-performance computing
systems such as clusters and Grids. It is based on a hierarchical design targeted at
federations of clusters. It leverages widely used technologies such as XML for data
representation, XDR for compact, portable data transport, and RRDtool for data
storage and visualization. It uses carefully engineered data structures and algorithms
to achieve very low per-node overheads and high concurrency. The implementation
is robust, has been ported to an extensive set of operating systems and processor
architectures, and is currently in use on thousands of clusters around the world. It
has been used to link clusters across university campuses and around the world and
can scale to handle clusters with 2000 nodes.

Ganglia is an open-source project that grew out of the University of California,
Berkeley Millennium Project which was initially funded in large part by the
National Partnership for Advanced Computational Infrastructure (NPACI)
and National Science Foundation RI Award EIA-9802069.
NPACI is funded by the National Science Foundation and strives to
advance science by creating a ubiquitous, continuous, and pervasive national
computational infrastructure: the Grid. Current support comes from Planet Lab: an
open platform for developing, deploying, and accessing planetary-scale services.

The ganglia system is comprised of two unique daemons, a PHP-based web frontend and a few other small utility programs.

The two unique daemons are Ganglia Monitoring Daemon (gmond) and Ganglia Meta Daemon (gmetad).
Gmond is a multi-threaded daemon which runs on each cluster node you want to monitor. It monitors changes in host state, announce relevant changes, listen to the state of all other ganglia nodes via a unicast or multicast channel and answer requests for an XML description of the cluster state.
Gmetad periodically polls a collection of child data sources, parses the collected XML, saves all numeric, volatile metrics to round-robin databases and exports the aggregated XML over a TCP sockets to clients. Data sources may be either gmond daemons, representing specific clusters, or other gmetad daemons, representing sets of clusters. Data sources use source IP addresses for access control and can be specified using multiple IP addresses for failover.
Ganglia PHP Web Frontend provides a view of the gathered information via real-time dynamic web pages. It depends on the existence of the gmetad which provides it with data from several Ganglia sources. Specifically, the web frontend will open the local port 8651 (by default) and expects to receive a Ganglia XML tree.

So, how to get ganglia running for you? The official installation and configuration guide and other information can be found here. I just won’t give an iterant and gash guide because ganglia is so easy and express to install and configure. From my experience, compared with other monitoring tools’ introductions such as Nagios, Cacti, Monit, Pandora FMS and so on, I think ganglia is conciser and easier to install and manage.(Honestly speaking, I haven’t used any one of them.) As you may see that, now or later, more functions which the other monitoring tools supplies may not included in gangila, but you can use your own scripts to achieve a few ones by using ganglia’s utility programs.
The official site gives some demo, go and check it if you are interested.

Simplicity is powerful. Lots of famous sites are using it. Yeah, Ganglia is worth a try. Maybe you will love it:-)