The number of ICAP server threads is one of the most important configurations regarding the ICAP server. Vendors have different recommendations for numbers for threads, and within the same vendor there can be different versions with different thread recommendations. The following is a general recommendation to use as a starting point. Test different thread numbers to determine the best value for your environment.
The following figure shows an example of how ICAP throughput changes with different thread configurations. In this example, the best value for thread number is 20.