Derby slows down after 1.2 million records

I'm using a Derby database, mass insertions slow down to 1/4 to 1/6 the speed once there are 1.2 million records (about 6 GB database size, one major table, other tables are tiny). Is that normal? Is there something I can do to tweak it and make it run faster? I compressed the main table. # Questions - Should I consider other databases? - How could I compare Derby's performance, with, say, MySQL in this kind of scenario? - Are there such comparisons already? (Running on Windows 7-based server R2, 16GB RAM, 8-core machine).