I'm making a decision about where to install what, and I need to know the following: If I have one SATA 3.0GB/s disk on the one hand, and two SATA 1.5GB/s disks combined as a RAID 0 drive on the other, which would be faster?
Since you have three drives, why not set up a Raid 0+1 array? The speed increase of 0, with the redundancy of 1. Its the best solution for a three drive set up. Use the largest capacity drive for your +1 drive so you don't limit you raid 0 capacity as much.
I'm not going to bother with mirroring, since 1) I want the extra space, 2) I'll store nothing important on the RAID 0 array (it'll just be to install games on) and 3) I can backup anything important manually.
Comments
Make sure you have backups, because RAID 0 guarantees eventual data loss without it.
This could be a good topic to look into further for general interest though.
The bus speed -- 1.5GB/s or 3.0GB/s -- has no bearing on the speed of the hard disk which typically maxes out around 100-130MB/s in ideal scenarios.
RAID SSD > RAID Raptor > SSD/RAID0 HDD > Raptor > HDD.
I'm not going to bother with mirroring, since 1) I want the extra space, 2) I'll store nothing important on the RAID 0 array (it'll just be to install games on) and 3) I can backup anything important manually.