Samsung F3 Spinpoint 1TB read and access time tests spikes

[QuickFire]

Take a look at my HD tune results:

Notice the downward spikes, and the scattered outliers in the access time test? What does this mean?

 

[andy5174]

My Seagate 7200.12 has more spikes on transfer rate but spike sizes are not as large as yours.

My WD Black has no spikes on transfer and fastest access time but average transfer rate is not as high.