DiskStore

Ehcache comes with a MemoryStore and a DiskStore. The MemoryStore is approximately an order of magnitude faster than the DiskStore. The reason is that the DiskStore incurs the following extra overhead:

• Serialization of the key and value
• Eviction from the MemoryStore using an eviction algorithm
• Reading from disk

Note that writing to disk is not a synchronous performance overhead because it is handled by a separate thread.

A Cache should alway have its maximumSize attribute set to 1 or higher. A Cache with a maximum size of 1 has twice the performance of a disk only cache, i.e. one where the maximumSize is set to 0. For this reason a warning will be issued if a Cache is created with a 0 maximumSize.

Replication

The asynchronous replicator is the highest performance. There are two different effects:

• Because it is asynchronous the caller returns immediately
• The messages are placed in a queue. As the queue is processed, multiple messages are sent in one RMI call, dramatically accelerating replication performance.

Statistics

Collection of cache statistics is not entirely free of overhead. In production systems where monitoring is not required statistics can be disabled. This can be done either programatically by calling setStatisticsEnabled(false) on the cache instance, or in configuration by setting the statistics="false" attribute of the relevant cache configuration element.