I would like to know if setting up raid 0 with regular hard drives would be a big performance boost or not, the SSD raid 0 seems to get more people that lean towards NO increase in noticeable performance. I have heard just the opposite is true with standard hard drives , that in fact a huge increase in performance is gained, noticed and measurable.
RAID 0 can potentially improve transfer rates, but it does nothing for access times. Faster transfer rates primarily help when copying or reading/writing large files, but they're not particularly effective in speeding up operations like booting or starting up programs because those types of tasks require a lot of small reads.
My personal experience suggests that RAID-0 might give you something like a 10% increase in boot speeds - that's a difference that you can measure but which isn't noticeable in day-to-day usage.
Whether to set up a computer using RAID-0 really depends on what you want to use it for, and how important your data is.
As a general rule, RAID-0 increases the Read and Write speed x the number of Disks you use. As an example if you use 2 Disks in RAID-0, both read and writes will be twice as fast, 3 Disks, three times as fast.
So, if your SATA-II HHD drives average 75-100 MB/s, 2 disks in RAID-0 will run 150-200 MB/s.
Just for comparison, recent tests showed SATA-II SSD's (Read and Write speeds are different) averaged 250 MB/s, SATA III (OCZ) run 468 MB/s. These are very general averages but give you and understanding and comparative numbers to think about.
So, if you are playing computer games, you will notice a speed difference for sure, if you are doing Excel spreadsheets you won.t
As sminlal indicated, Raid0 will boost sequencial read/writes which gives a nice boost to operations that are sequencial in nature. As both above pointed out operations that read/write small files do not benifit. Reason as sminlal pointed out - Normal Raid0 does nothing for access time.
You can improve access time in a Raid0, but lose disk space. You can short stroke the drives. For example, 2 x 1 TB drives. Instead of creating the whole 2 TBs as a volume you would only use 600 Gigs for a volume and NOT use the remainder of the disk. I short stroked a pair of WD 640 drives and it cut the access time from approx 11.6 mSec to around 9.5 mSec. NO wheres near and SSD, but it was faster than a normal Raid0 setup.
Just a note to point out that you can cut access time via short-stroking whether you use RAID-0 or not. It improves access times (but not transfer rates) just as well on individual drives - which is to say that it's measurable but probably not particularly noticeable.