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I need to study about high-availability and load balancing of a web server. My choice was IIS, cause of I'm familiar with it. I have some questions to ask:

  • Which is the first version of IIS that supports high-availability? Load balancing?
  • Is there some books/resources that provide a complete information/knowledge about HA/Load-balancing on IIS? (would be great if it is free :D )

Thank you so much!


locked by HopelessN00b Jan 12 '15 at 16:20

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closed as off-topic by HopelessN00b Jan 12 '15 at 16:19

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up vote 3 down vote accepted

It's the OS that needs to support HA and loadbalancing. Windows NT was the first to support NLB and clustering.

as far as resources go here's a list based on OS types

Network Load Balancing: Frequently Asked Questions for Windows 2000 and Windows Server 2003

Network Load Balancing (2008)

Failover Clusters

Server Clusters: Frequently Asked Questions for Windows 2000 and Windows Server 2003


If you're using IIS7, or you can install IIS7 on a front end pair of servers, then consider Application Request Routing (ARR) link text is a great place to start. I'm sure there are some good books out there although I don't know of any focusing on HA for IIS.

All versions of IIS 'supported' high-availability. It's the load balancer on the front that does the real work. ARR is an inexpensive (you can use Web edition, and ARR itself doesn't cost anything) but very high performing solution.

For keeping the IIS configuration in sync, IIS7 has some huge improvements with 'shared configuration'. Previous versions would work but they aren't near as convenient as IIS7.



  • None. IIS does not support high availability at all, and no load balancing. This is all done outside IIS. if yo use OS items, it is NLBS (Network Laod Balancing). I am NOT sure when this was introduced, but it goes back a LOT - possibly before 2000. You may argue you always could have multiple IIS instances.... at different IP addresses. Correct - but that is not an IIS feature. it requires no cooperation by IIS at all.
  • MS documentation ;)

In general, load balancing is done outside of the web server at a front end / router level, or - less so - at a OS level.


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