increase capacity adding sas disks to md3620f

Hi.

I have an MD3620F with two groups of SAS disks: 600GB 10Krpm HotPlug and 1TB 7,2Krpm HotPlug.

Now, the manager of Powervault says: "Physical disk predicted failure detected Event Priority: Warning Component Type: Physical Disk Component Location: Enclosure 0, Slot 0" and I understood that disk 0 - SAS 600GB 10K is going to be unusable.  So, I ordered a couple of SAS 600GB disks to substitute the predicted failure.  Just a problem occurred.  My vendor said that SAS 600GB 10Krpm are now unavailable and he proposed a disk having the same capacity but 15Krpm instead of 10Krpm.

My question:  is it possible to substitute in MD3820F a SAS disk with 600GB 10Krpm with a 600Gb 15Krpm?  Thanks.