Interactive simulation
Click "Random read" and watch how each drive locates the same piece of data. Animation pacing is slowed down for visibility; the millisecond readouts are realistic typical values for a 7200 RPM HDD and a consumer NVMe SSD.
HDD
mechanical seek
idle
— ms
SSD
electrical address
idle
— ms
Each HDD read pays two mechanical costs: seek time (swinging the arm to the right track) and rotational latency (waiting for the platter to spin the target sector underneath the head). An SSD pays neither — the controller addresses any flash cell directly, so scattered random reads cost about the same as sequential ones.
