I first installed the RAID drivers, obviously, and then when installing Windows, I made a 60GB partition to boot from. Windows installation automatically formats this drive to have 4kb clusters. I also made the other 410GB another partition, which was left unformatted.
Once windows was loaded, I formated the 410GB partition (E) with 64kb clusters by running "format e: /FS:NTFS /A:64KB" in a command prompt.
As you'll notice, as file size gets larger, the 64kb cluster drive starts to pull away... this cannot be attributed to the position of the partitions on the drives, since the C drive is actually on the outermost portions of the disk. At any rate, here are the results:
C (4kb clusters): http://s42.yousendit.com/d.aspx?id=0...I3NAK1DP0JN36K
E (64kb clusters): http://s48.yousendit.com/d.aspx?id=1...23R79LSA4SIVNX
It would've been really nice to get a 5th drive so that I wouldn't have had to partition the array, but it's working pretty nicely.
More on cluster sizes here:
If you are going to store multimedia stuff that is usually huge in size, make cluster bigger to increase a performance.
The choice of cluster size has an impact on real-world performance, though for most people it is not all that significant. In a nutshell, larger clusters waste more space due to slack but generally provide for slightly better performance because there will be less fragmentation and more of the file will be in consecutive blocks.