I need a database system which is suitable for time-series data.
That is nearly all tables in the DB are flat tables with very little
relationships.
I used to use Ms-Jet but the 2Gb size limitation was getting to be problem.
Swithcing to ms-SQL was expensive and hard but it worked.
The problem is that ms-SQL is VERY SLOW to read and write large blocks of
data.

If I just read/write the data from/to text files myself it goes more than 5
times faster.
I'm guessing that all the overhead is because of the relational work that
ms-SQL does.

Is there a DB system which is designed for a collection of unrelated tables
which does not have a size limit?

From what I have seen, I suppose anything is going to be faster than ms-SQL.

Ernesto