How to choose database management system?

Question

Basic requirements

1. Fault tolerant (ex. has to work even when an entire data center goes down)
2. Maximum number of records are about 1-5 billion
3. Has to work properly and comparatively fast under high load
4. Compatible with JavaEE
5. Prefer relative DB but in general it doesn't matter
6. Free of charge

Do you have any ideas?

Answer 1

Wikipedia has an extensive list that compares many RDBMSs - take a look.

PostGresSql is a good free option.

Answer 2

Well frankly if were designing something like that, I'd go for Oracle or SQL Server because that's where most of the people who have expertise in high performing databases are. In a system like that you need first and foremost a good DBA who is experienced in high performance, low down-time systems. These are complex to design and set-up properly and there is no substitute for hiring an expert before beginning the design phase as database design has a huge impact on performance.

Neither of these is cheap, but you want Enterprise level performance, you have to pay for it. The DBA won't be cheap either, but he or she is a critical element to the success of this type of project and the DBA needs to be in one the design phase to keep you from shooting yourself in the foot designing EAV tables or using cursors instead of set-based logic.