since my HAF X case has lots of space, I went ahead and put 5 drives in it. 2 SSD- both are OCZ Vertex 2. These 2 are both 200 GB in size so that's 400 GB. My O.S is in one of these. They are small. The rest are all HDDs. 2 are 2 TB in size, spin at 7200 rpm, and are from W.D and the last one is 600 GB in size, and it's from HP, but it spins at 15k RPM, which is rather impressive but was crazy expensive!!!. Since my computer is rather new, i've barely filled 100 Gbs. Oh yeah, after the formatting, all the drives don't reach to their said capacity.