For IIS to scale out to multiple servers and remain manageable, it needs to ensure that the least amount of effort possible is required for each individual server. Ideally, you should be able to manage a large server farm with no more effort than you would take to manage a single server.
One of the key enhancements that was introduced in IIS 7.0 is Shared Configuration. It allows the configuration to be generalized so that everything unique to each server is removed. Then, that one configuration file can be shared by all the servers. With that in place, whenever a change is made to IIS, that change is essentially applied to all the servers at the same time. There is no longer any manual work to make changes to multiple servers or to manually run scripts to keep the servers in sync.
Surrounding Shared Configuration are many other smaller enhancements—for example, the ability to make the configuration file completely machine neutral, support for system environment variables in the configuration files, and a configuration infrastructure that allows multiple servers to read and write to the same configuration file without any locking or sharing violations.
Sharing the IIS configuration is by no means the only consideration needed for managing a highly available web farm, so we will also look at the other aspects of setting up and managing your web farm.