Over a long period data files fill up in the activemq-data/borker1/data/journal directory. Scenario is single queue, persistent producer and consumer, consumer periodically stalls to allow messages to build up in broker.
Problem appears to be related to message ack before async message store gets a chance to persist messages. Reference to active data file remain which stops them being cleaned up by the periodic checkpoint.
This limits the available up time of the broker with large volumes of messages as excessive amounts of disk space are consumed.
Using syncOnWrite=true or setting a AMQPersistenceAdapter.maxCheckpointMessageAddSize=0 will help avoid the problem, both of which will effect performance.