Adaptation Policies
Policies specify system states and how to react to them
- high-level specification: independent of “schema” of system, object/node identity
- that knowledge is encapsulated in policy compiler
- Examples
- self-maintenance and availability
- if overall free disk space is below 10%, compress all but one replica/version of least-frequently-accessed data
- if any disk reports more than 5 errors per hour, migrate all data off that disk and shut it down
- invoke load-balancer when new disk is added to system
- performance tuning
- place large, sequentially-accessed objects on outer tracks of fast disks as space becomes available