ObjectDB database files are usually smaller than database files of other Database Management Systems (object databases and relational databases) but additional internal compression is still possible.

Usually smaller files are also faster because less I/O operations are required and memory cache can be used more efficiently. On the other hand, compression and decompression consumes CPU time. So the effect of using compressed ObjectDB database file on performance is unknown yet.

ObjectDB Support
ObjectDB - Fast Object Database for Java (JPA/JDO)