Multiple servers in a three-tier farm configuration

I have been assigned the task of designing and implementing a SharePoint farm that will be used by hundreds of users.  Taking redundancy and performance into consideration I have chosen a three-tier topology.

This farm will consist of three tiers: Web tier, Application tier and Database tier.  This topology is typically used for medium and large farms as it provides the most efficient physical and logical layout to scale out or scale up, as you can see in the Visio diagram below:

The Database Tier

This will be a Microsoft SQL Server 2008 R2 cluster.  This will ensure high availability of the Central Administration, Farm content, Search, Crawl and Property databases.

The Application Tier

These servers will host the Central Administration, Search Administration component and Crawl component.

The Web Tier

These web servers will be load-balanced using the NLB feature in Windows 2008 Enterprise Edition to host the query component.