BigMemory permits caches to use an additional
type of memory store outside the object heap, called the "off-heap store." It's available for both distributed and standalone use cases.
The off-heap store, which is not subject to Java garbage collection (GC), is 100 times faster than the DiskStore and allows extremely large caches to be created. Because off-heap data is stored in bytes, there are two implications:
Only Serializable cache keys and values can be placed in the store, similar to DiskStore.
Serialization and deserialization take place on putting and getting from the store. The theoretical difference in the overhead associated with serialization and deserialization disappears due to two effects:
the MemoryStore holds the hottest subset of data from the off-heap store, already in deserialized form, and
when the GC involved with larger heaps is taken into account, the off-heap store is faster on average.