Question : Problem: Mixing 15k drives with 10k drives?

I have a Poweredge 2600 server with a PERC4/DI RAID controller.  I am currently running 3 Fujitsu 73gb 10k RPM drives.  I would like to add 2 more drives, 1 as a hotswap, and 1 for extra space.  

My question is this, is is ok to mix 15K drives with 10k drives?  I found a better deal on the 15k drives with a better warranty vs. the 10k drives.  Here are the links.

http://www.scsi4me.com/product_info.php?products_id=1432&osCsid=74febca516c330c5519158f104c3dea8
http://www.foxtec.com/products/view.asp?ID=4842

I have heard that the 15k drives will only run at 10k but otherwise there is nothing wrong with this.  I have also heard that when the 15k drives come down to 10k it can cause issues.  Any help would be greatly appreciated.
 

Answer : Problem: Mixing 15k drives with 10k drives?

if they are not in the same raid array it should be fine, if you put them in the same array as the 10k drives you will have issues. I have yet to see a raid arry with a mix of 10 and 15k drives work properly. The configuration i would suggest if you buy the 2 15 k drives is a raid 1(os) on the 2 15ks and a raid 5(data) on the 3 10ks. If possible for performance split the backplane and use seperate channels for the raid arrays since the perc 4/di is a dual channel controller.