WAN optimization is available on FortiGate models with internal storage that also support SSL acceleration. Internal storage includes high-capacity internal hard disks, AMC hard disk modules, FortiGate Storage Modules (FSMs) or over 4 Gbytes of internal flash storage. All of these storage locations can provide similar web caching and byte caching performance. If you add more than one storage location (for example, by creating multiple partitions on a storage device, by using more than one FSM, or by using an FSM and AMC hard disk in the same FortiGate unit) you can configure different storage locations for web caching and byte caching.