Understanding Hard Drives and Optical Drives: Storage Solutions
Hard Drives: Traditional Storage
The hard drive is the primary means of storing large amounts of information on a computer. It belongs to a type of memory called mass memory. Although significantly faster than other storage media, it has some disadvantages. External hard drives with USB, Firewire, or eSATA interfaces offer portability. However, even though an external hard drive is portable, it’s not always the best way to transport information because it’s composed of mobile and sensitive components that shouldn’t be moved excessively or with jerky movements while in use. This is a significant disadvantage for laptops, preventing them from being fully adopted in environments like cars. Despite this limitation, hard drives remain the most economical, highest-performing, and largest-capacity storage option.
Formula to Determine Hard Drive Size:
Number of cylinders x Number of heads x Number of sectors x 512 bytes/sector
Partitions: Dividing Your Hard Drive
A group of consecutive disk cylinders treated by the operating system as a separate storage unit. Each hard disk is a distinct physical drive. A single physical disk drive can contain multiple logical drives. A hard disk can have up to 4 partitions, with a minimum of 1.
Types of Partitions:
- Primary Partitions: These can boot the computer and operating system. One primary partition should be active (pre-selected by default).
- Extended Partitions: Only one extended partition is allowed, and it cannot be used to boot the operating system. Even if an operating system is installed here, the computer cannot run it. It cannot be active in the partition table.
Optical Drives: Secure Data Storage
Optical drives are more secure than magnetic drives. Data is recorded with error correction codes. Information is read by laser, allowing for more information to be stored in less space due to its increased accuracy.
Physical Methods of Recording:
- Degradation of Layer: A mold is created through a process like photo development (light on a photosensitive layer, where light areas become ridges or holes). Matrices are obtained from the mold to create multiple disks (negatives). The aluminum layer is constructed from these matrices, degrading the ridges and valleys. Finally, the plastic layer is applied.
- Change of Phase: A thin layer of gold or aluminum with a transparent stain on it. The laser can cut through the clear coat and reflect off the metal. If the laser strikes with significant power, it can burn the dye, leaving it dark (blue, green, gold, black). During reading, the laser beam is not reflected in the burned spots. The black dots may represent a logical “0,” and transparent spots a logical “1.” Once the dye is burned, it cannot be reused to record other information.
- Phase Change Dual: Similar to the above, but the dye layer is a metal alloy. A high-power laser can change its color and reflective properties from transparent to dark. The reverse change can also occur with repeated stressing.