What method is best? It really depends on your application and some other surrounding factors. Each method is good though and would probably satisfy requirements regardless of configuration. Especially if you are closely monitoring each server node with an external tool (other than directly from load-balancing switch). So, with external monitoring you can confirm that all server nodes are operating without error and within reasonable speed thresholds that have been set.

Also, remember that, regardless which traffic algorithm is chosen, if a node goes down, traffic is sent to other nodes. And when a node comes back online, it can automatically be placed back into webfarm and start getting client requests again.

Clustered hosting does require some consideration of how state is managed within applications, which will be covered in a future article.

Happy hosting!

~Brad

Brad Kingsley is President and Founder of ORCS Web, Inc. - a company that provides managed hosting services for clients who develop and deploy their applications on Microsoft Windows platforms.

* Round-robin: Each node gets a request sent to it "in turn". So, node1 gets a request, then node2 again, then node1, then node2 again. * Least Active: Whichever node shows to have lowest number of current connects gets new connects sent to it. This is good to help keep load balanced between server nodes. * Fastest Reply: Whichever node replies faster is one that gets new requests. This is also a good option - especially if there are nodes that might not be "equal" in performance. If one performs much better than other, why not send more requests there?

In any of these scenarios switch will also detect if a node were to fail. So, if svr1.orcsweb.com was taken offline for maintenance - or it had a critical failure - switch would detect that and only send traffic to svr2.orcsweb.com. And since clients always access site via main URL (not node names) they have no idea that one of nodes is down - application continues to serve client requests seamlessly.

Besides high-availability (continuing to satisfy requests during a failure), a webfarm also gives an application a higher level of scalability - ability to handle more and more load. If load increased on application to point where performance started to degrade, more nodes could be added to webfarm (again, without clients noticing), giving ability to handle potentially unlimited levels of traffic (just keep adding nodes!).

Of course there are a lot of factors surrounding proper support of a webfarm - switches, fail over between switches (don't let switch be a single point-of-failure!), replication of content, synchronization of server changes, synchronization of application changes, etc, etc.. But a good system administrator (or experienced hosting company) can help address all of these issues for you.

By way, I need to slip in a plug for a related service we offer :-) Webfarm hosting starting as low as $199/month! Check it out at: http://www.orcsweb.com/WebFarm.aspx

Hopefully this has been a good introduction to webfarms for you, and hopefully I've properly communicated enough of benefits for you to consider this as a hosting option for yourself. With rates now down to affordable levels - why not get this additional layer of protection?

Happy hosting!

~Brad

Brad Kingsley is President and Founder of ORCS Web, Inc. - a company that provides managed hosting services for clients who develop and deploy their applications on Microsoft Windows platforms.