Calculate overall BranchCache results
Updated: March 10, 2010
Applies To: Windows Server 2008 R2
On Content-01, open Windows Performance Monitor to review statistics after performing all of the tests in this guide. In the topic Configure Content-01 with BranchCache performance counters, you added the following BranchCache kernel mode counters:
Client Cache Miss Bytes. This counter specifies the number of bytes of content provided by the content server because a client was not able to find the content within the local branch. In other words, this counter increases when the content server sends content information to client computers and the client cannot find the content in the branch office.
Hash Bytes. This counter specifies the number of bytes of content information (also called hashes) that the content server has provided to client computers.
Projected Server Bytes Without Caching. This counter specifies the number of bytes that the content server would have provided to client computers if not configured as a BranchCache content server.
Server Cache Miss Bytes. This counter specifies the number of bytes of content that the server provided to client computers because the server did not have content information (also called hashes) available for that content. In other words, this counter increases when the content server cannot send content information to the client because the content information has not yet been generated by the server. For example, when Client-01 requests content from the server, the server has not yet generated content information. The content server sends the actual content to the client, the Server Cache Miss Bytes counter value increases, and the server then generates the content information for the requested content. The next client to request the same content (Client-02) will then receive both the content information and the content from the content server.
You can calculate the total WAN bandwidth savings – or the amount of content accessed from the client cache rather than from the content server - across all BranchCache-enabled client computers that accessed content on Content-01 during your tests by using the following formula: Total bytes saved = Projected Server Bytes Without Caching minus Client Cache Miss Bytes minus Server Cache Miss Bytes minus Hash Bytes.
Example calculation using BranchCache kernel mode performance counters
The illustration below provides example statistics for these counters after running the tests in this guide.
Using these statistics as the basis for the calculation, you can discover how much content that client computers accessed from each other rather than over the WAN link from the server:
554,838.000 (Projected Server Bytes Without Caching) – 184,946.000 (Client Cache Miss Bytes) = 369,892.000 (Subtotal 1)
369,892.000 (Subtotal 1) – 184,946.000 (Server Cache Miss Bytes) = 184,946.000 (Subtotal 2)
184,946.000 (Subtotal 2) – 396.000 (Hash Bytes) = 184,550.000 (Total bytes saved)