Raid 0+1 and Different Disk Speeds/Sizes

I just got a new (used) Mac Pro with an Apple raid card and 2 300GB 10k hard drives. I want to setup the 2 10k's in raid 0, but have a raid + 1 using two other drives (2 500gb 7200) to give me a 600GB raid 0+1 array using the 4 disks

My question is: Will using the slower (and bigger) drives for the mirrored part slow down the fast access given by the 2 10k drives? I figured that the mirrored drive is for writes only and that the internal write cache would handle it, but I am not sure.

EDIT
All 4 drives are SATA
2x300GB Western Digital Velociraptor 10,000 RPM drives
2x500GB Hitachi Deskstar 7200 RPM Drives

Solution 1:

I think you misunderstand how RAID 0+1 works. And you'll actually want to do 1+0, it performs the same, but is more fault tolerant in larger sets, so if you ever grow you'll have better protection.

RAID 0+1 isn't having a RAID 0 that's contents are mirrored to a separate RAID 1 automatically. In a 4 disk RAID 0+1 there are two RAID 0 sets that are then mirrored with eachother. In 1+0 there are pairs of RAID 1 mirrors that are then striped. In either RAID level, you lose 50% of the raw capacity.

In either case you are limited by the smallest size and speed. It sounds like what you may want to do is RAID 1 the 10k drives and create a separate RAID 1 out of the 7.2k drives and skip the striping.