Raid 0 is used for performance only: there's no protection against data loss. Imagine that instead of saving a whole file of 100MB in one disk, you'll be saving 50MB in each disk simultaneously.
For example, in a rough approximation, assuming that one HDD is really twice as fast as the other: it would save 50MB in the faster disk in x seconds and in would take 2x seconds in the slower one. Since it's done at the same time, the total saving time would be 2x seconds for 100 MB.
If you saved the same file just in the slower disk, you would spend 50MB -> 2x, 100MB -> 4x seconds. In the faster one, you would spend 50MB -> x, 100MB -> 2x.
So, using RAID 0 you'll use both disks at the same speed you would get if you had only the faster disk available.
Problems: this is a rough approximation. HDDs have access time, data burst rates, caches, etc., that impact this simulation. And it also assumes that your motherboard really provides you with the real RAID 0 abillity, so that your data won't be bottlenecked somewhere.
Remember that raid 0 doubles your problems in case of fail: since all your data will be split in two HDD, one of them failling means that you loose everything, as probably recovering half file won't be usefull.
Suggestion: why not put the most used files (like the OS, swap files, etc) in the faster drive and use the slower drive to save files that you don't need the better performance? Ex.: music files, videos, etc.
What's your question? Does it give more space? Is it faster? Or is it compatible? It's kinda hard to see what you're asking here – James Mertz – 2011-09-14T14:47:55.700
I'm sorry it was unclear - it was a pretty broad question, because I was unsure of all of it really, speed, the space, the general things to be aware of when doing it with the hdds in question. but the answers I got were very informative, so I'm good :) – Dynde – 2011-09-14T15:04:01.063