Abnormal start and stop of SATA HD. I just intalled this HD on my new DELL XPS 420 as a slave

Question

I just intalled this HD on my new DELL XPS 420 as a slave drive. It works fine, but when I'm not accessing it, it continues to spin up and stop every minute or so. I am concerned that this puts a strain on the motor and will speed up wear of bearings. Is it normal or is it defective? [e-mail]