Migrating to a Cherwell Server Farm

Establish a Baseline

Start by isolating the web and application servers from all the other servers. Your scheduling or e-mail servers might be using the resources needed to serve the Desktop Client and Web Applications. Create a single-server environment where the web and app server have a dedicated machine and all other services are together in one machine.

Calculate the Number of Servers Needed

To calculate the number of server, have a few data points ready:

• USER_POPULATION: What is your total number of Users?
• CONCURRENT_USER_PEAK: What is the peak number of concurrent Users I want to support?
• USER_LOAD_THRESHOLD: At what point do you start experiencing slowness?
• MACHINE_FAILURE_TOLERANCE: How many machines do I expect could go down at the same time?

Example: You have an environment with three thousands Users, a typical peak usage of one thousand Users, and the system performance starts slowing at around three hundred Users.

Based on the calculations above, you would need six servers to be able to comfortably serve a typical peak User population, but you would need 69 servers to support 100 percent of Users coming online at the same time.

The calculation above does not take into consideration if the Users are Web or Desktop Client Users. There is a possibility that the environment is heavy loaded on one type of client. If this is true, start with a configuration where both application and web servers are distributed across the LOAD_BALANCED_SERVERS_REQUIRED. If that is insufficient, select one of two strategies:

• Add more hardware, keeping web and application servers on the same box. See Minimal Scenario.
• Separate the application and web servers and perform the above calculation for the DIFFERENT load that you expect on each platform. See Maximum Distribution Scenario. At the end there is a number of LOAD_BALANCED_SERVERS_REQUIRED for web and application.

Example: Migrating from large servers to commodity hardware

If the core machine is 8 2.4gHz, and you want to use commodity hardware instead, consider using two 4-core 2.4gHz machines, or three 3-core 1.8ghz machines. The calculation is not perfect science, but the cost saving should allow you to err on the side of caution.

If the original LOAD_BALANCED_SERVERS_REQUIRED is six, consider a multiplier of two or three depending on the commodity hardware you chose to use, for a total of 12 or 18 commodity machines instead of six servers.