To accelerate and optimize disk access and to provide better throughput and less latency, web caching uses provisioned memory to reduce disk I/O and increase disk I/O efficiency. In addition, web caching requires a small amount of additional memory per session for comprehensive flow control logic and efficient traffic forwarding.

When web caching is enabled you will see a reduction in available memory. The reduction increases when more web caching sessions are being processed. If you are thinking of enabling web caching on an operating FortiGate unit, make sure its memory usage is not maxed out during high traffic periods.

In addition to using the system dashboard to see the current memory usage you can use the get test wad 2 command to see how much memory is currently being used by web caching. See “get test {wad | wccpd} <test_level>” for more information.