AFS Version 2

Callback

AFSv2 introduced the notion of a callback to reduce the number of client/server interactions. A callback is simply a promise from the server to the client that the server will inform the client when a file that the client is caching has been modified. By adding this state to the system, the client no longer needs to contact the server to find out if a cached file is still valid. Rather, it assumes that the file is valid until the server tells it otherwise; notice the analogy to polling versus ...