Hot Cache: The Hot Cache is what you would see on a BigIP LTM device if you were to use an HTTP Class with RamCache enabled, the hot cache (RamCache) allows some limited caching functions and is bundled as one of the features built-in to the BigIP LTM device. This type of caching provides functionality much like a caching proxy server would in that the LTM will stand in proxy to the application server and request content on the client’s behalf – all normal application-generated caching rules apply however. Hot Cache maintains an in-memory cache of objects throughout their lifecycle.

Smart Cache: The Smart Cache is a Hot Cache on steroids, in the middle of ‘roid rage. Smart Cache is what happens when you add the Web Accelerator (WA) module into a BigIP LTM. Smart Cache is a little different from hot cache in that it not only maintains an in-memory set of the most used objects and objects which are not intelligently cached via IBR, but also does disk-based caching of other objects which have not yet been deemed invalid (IBR objects). The disk cache allows the WA to perform intelligent caching, allowing some objects to remain cached forever even if they never change on the server. The implications are insane especially for fairly static applications/sites.

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