[dba-Tech] Replacement Hard Drive for Raid 5 Array

One of the drives in a 3 drive Raid 5 Array on our server died overnight.
Fortunately, we have a spare which is being rebuilt as I write. I went
looking for a replacement for the spare, since this is the second drive to
fail, and discovered that the same drive is no longer available: 73GB, 10K
RPM, 80-pin SCSI U320.
What we can get is the same drive at 15K RPM. Other than spindle speed, the
specs are the same.

My question is, will there be a problem running drives with different RPMs
in the same array? 

Thanks,
James Barash