MOSS 2007. The smallest server farm for a company (In my opinion)

The smallest server farm that builds in redundancy consists of four servers:
• Servers 1 and 2: Web servers and query role installed on both computers. Additional application server roles, such as Excel Calculation Services, can be installed on one or both servers.
• Servers 3 and 4: clustered or mirrored database server.

With a four-server farm, you must carefully choose where to deploy the index server role. The query role cannot be deployed to both the index server and another server in the farm to achieve redundancy. This is because, when the index role is installed on the same server computer as the query role, the index role no longer propagates content indexes to other query servers. Consequently, if you install the index server role to one of the Web servers, you lose the ability to host the query role on both Web servers. You can install the index role on the database server, achieving redundancy of the query role on the Web servers. However, the performance of the database server will be affected, particularly when content is being crawled.
Additional application server roles, such as Excel Calculation Services, can be installed on one or both Web servers, depending on performance and availability requirements. In the previous diagram, additional application roles are deployed to only one of the servers in both Option A and Option B.
In Option A, performance is optimized if the Web server that is not hosting the combined index and query roles hosts the other application roles.
In Option B, the topology is optimized for user requests and queries. Performance of the other Web server