my hard drives say 300 MB/s, my mobo says SATA II 3Gb/s ... are they compatable? Is that the same or is one faster?
Also I see some SATA cables say 300 MB/s, some say 150 MB/s and some say "maximum 150 MB/s" ... but when I called Western Digital they said that they are all the same and there is no difference in the transfer speed on the SATA data cable, only the drive itself and the mobo or card.
I go the drives (4 250gig all the same model) I was going to go raid 0+1, but the guy at Micro Center said to go raid 5. 0+1 looks like it might lose more space, but be more secure. I just had a brand new hd crash with 6 months of purchase and it was almost full so I worry about this again. Wouldn't 0+1 be safer and easier to rebuild? Also if me mobo dies... can i just connect these 4 drives to any raid controller that supports the raid array I choose or would I have to use the same mobo?
Western Digital is correct, the cables are not speed rated and any will work. The only exception is external SATA (eSATA) cables for external HDD's which have a different connector and require more shielding because the cables can be 10 feet long. eSATA cables are sometimes (erroneously) referred to as SATA2 cables.
Your hard drives will work fine with your motherboard. Notice that 3Gb/s and 300MB/s have different B's. A Byte consists of 8 bits. I could be wrong but 3Gb/s = 3000Mb/s = 375MB/s = ~300MB/s (I could totally be blowing smoke here, no flames please). Anyway, just be confident that your HDD's will work with your motherboard. The two ratings are thrown around interchangeably, but in the end it doesn't really matter because HDD's cannot transfer rates at those speeds anyway.
As for the RAID 0+1 vs. RAID 5? I won't pretend I know anything about either so I won't give any advice. Maybe look it up on wikipedia or someone else here has some tips.