Lets start with a typical drive design. Nowadays, hard drives come in different sizes, or form-factors, and use 3.5-inch, 2.5-inch, 2-inch, 1-inch, and other disk diameters.

Every hard drive has one or many platters (which store magnetic data), usually twice as many sliders with magnetic heads (to read and write data), an actuator arm (to hold the suspension with the slider at the end), and a voice-coil actuator (to move the actuator when the head is accessing data). The drive is connected to the computer via the interface connector.

For some reason (unknown to us!), drive manufacturers always present their drives with the cover removed (see picture on the left). Since, the basic design of all the drives is quite similar, it is not clear what exactly they want us to see. The only important difference one can see from the picture of the opened drive is if its head is parked closer to the center of the disk (on the disk surface) or on the outer diameter of the disk (on a special ramp). This difference represents a major difference in drive design, ideology, and technology: the difference between contact start-stop drives (CSS) and load-unload (L/U) drives.

Nowadays, the CSS design can be found in drives for most Desktop computers, many of mobile drives, and many of the drives for high-end servers.

L/U technology is gradually displacing CSS in the mobile drives and servers. L/U design prevents slider / disk contacts (except for the accidental ones) and increases drive durability. A dehumidifier bag in the upper left corner serves the need to reduce humidity inside the drive. High humidity enhances adhesion (stiction) between the sliders and the platters. Sometimes the stiction becomes so high, that the drive spindle is unable to rotate the drive without causing mechanical damage to the suspension / slider system resulting in data loss. Another reason why lower humidity is desirable is to reduce corrosion of the metal surfaces inside the drive.

Now, lets take a look at the slider / disk interface of the modern drive.

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