The "poor man's raid" option as mentioned above is not viable because the ST350176LC drives are 1.6" half height models which are too thick to fit in 1U cases properly, and outfitting them in a 3U or 4U case would make colocation costs too high.
One dosent have to follow that article to the letter, just use it as an example of how one can set up a RAID array cheaply. There are Seagate and IBM drives available that fit in a 1U case, personally I would recommend a 3U case for the database server considering the number of harddrives likely to be used and the integrety needed in data storage. Using a 1U is just asking for bearing failure in the harddrives, considering the lack of proper heat dissipation in such a design.
For the database server:
IBM xSeries 34x like the xSeries 346, but perhaps the x340 which would be available cheap on eBay, put 5x 73GB drives in it and a ServerRAID or Adaptec RAID card in it and you are good to go. Look for at least a single 1.2GHz or dual 1.0GHz, that line of servers will have Xeons.
For the webserver:
A 1U unit, like a x330 or something like that, single harddisk.
Link the two using a crossover ethernet cable, both should have dual ethernet.