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Linuxtag 2008
Shared Storage Cluster
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Linux Virtual Server
A Linux Virtual Server is highly scalable server consisting of a cluster of computers equipped with Loadbalancers. Towards the user a Linux virtual server behaves like a single high-performance server.
Core of the Linux Virtual Server [1] is a server working as a
router, called Director. The Director has ideally have at
least two network cards, one for the public network, one for the
private. Requests to the service IP are redirected to the Real
servers according to the configured rules.
When any real server is brought up, is also configurable, it may be difficult to ensure that a client requests always on the same real-server, but also all the real servers in roughly the same burden.
The Director also monitors its Real servers and takes unreachable Real servers out of its routing tables, adds returned automatically.
To ensure reliability one would have a second Director in hot standby mode, that takes over the service IP when necessary. Are the Real servers redundant, too, the result is an inexpensive, high available and scalable cluster.
Links:
[1] http://www.linuxvirtualserver.org/