Which hardware ?

Hi,

I need to install a 8.3 database and was wondering which hardware would be
sufficient to have good performances (less than 30s for slowest select).

Database size: 25 Go /year, 5 years of history
One main table containing 40 million lines per year.
Batch inserts of 100000 lines. Very very few deletes, few updates.

30 other tables, 4 levels of hierarchy, containing from 10 lines up to 20000
lines.
5 of them have forein keys on the main table.

I will use table partitionning on the year column.

Statements will mainly do sums on the main table, grouped by whatever column
of the database (3-5 joined tables, or join on join), with some criterions
that may vary, lots of "joined varchar in ('a','b',...,'z')".
It's almost impossible to predict what users will do via the webapplication
that queries this database: almost all select, join, group by, where...
possibilities are available.

Up to 4 simultaneous users.

I'm planning to host it on a quad xeon 2.66Ghz with 8Go of DDR2, and a dual
(RAID1) SATA2 750Go HD.
Perharps with another HD for indexes.

Do you think it will be enough ?
Is another RAID for better performances a minimum requirement ?
Will a secondary HD for indexes help ?

Which OS would you use ? (knowing that there will be a JDK 1.6 installed
too)

With 5 millions of lines, the same application runs quite fast on windows
2000 on a single P4 2.8 GHz (very few statements last more than 10s, mostly
when concurrent statements are made). Each statement consumes 100% of the
CPU.

thanks for advices.