“With so many commercial Linux clustering products on the
market, administrators may be surprised to learn that high-quality,
open source clustering solutions can provide functionality similar
to that of commercial clustering products at little or no
cost. Projects such as Red Hat’s Piranha (from the High
Availability Server Project) and Ultra Monkey use the Linux Virtual
Server Project’s Linux Virtual Server (LVS) technology to provide
complete balancing of services among a group of servers according
to a variety of scheduling algorithms. Composed of several
components, LVS supports most of the features provided by
commercial packages such as PolyServe LocalCluster Enterprise and
Turbolinux Cluster Server, although it does require more technical
know-how to achieve the same results.”
“LVS’s core kernel code, ipvs, routes service requests from
clients to the servers that provide the services. It also keeps
track of the requests and the connections associated with them to
ensure that they’re delivered to the appropriate servers. Used in
tandem with monitoring software, ipvs provides failover services
for servers that are down as well as distributed management and
load balancing.”
“LVS uses several load-balancing algorithms, including round
robin, least connections, weighted round robin, and weighted
least-connections. LVS also supports a variety of different network
architectures. The system’s main disadvantage is that it’s
significantly more difficult to install and configure than most
commercial offerings such as Piranha and Ultra Monkey, both of
which offer easier installation and configuration.”