If you have modern flight sims with huge photoreal textures, there is no hard drive large enough. I have DCS World, DCS World beta, P3d with a lot of ORBX upgrades (including the huge Netherlands upgrade), Aerofly FS2 with some ORBX (most notably the huge Netherlands upgrade), FlyInside Flight Simulator, IL-2 Battle Over XXX, etc. A 500 GB SSD plus a conventional 2 TB RAID 1 array were not enough. Adding a 500 GB SSD has allowed me to upgrade a few sims stuck on the much slower RAID array, but I really need a whole lot more SSD space to load and run these sims without long load times and stuttering.