External Hard Disk

External

hard disk

drive

An external hard disk drive is a type of hard disk drive which is externally connected to a computer, and may be portable. External hard disk drives are connected to the computer using a cable which is compatible with Small Computer System Interface (SCSI), Integrated Drive Electronics (IDE), Universal Serial Bus (USB), IEEE 1394 (Firewire), CAT-3 or CAT-5 cable (Ethernet), eSATA or other bus standards.

Structure and design

The internal structure of external hard disk drives is similar to normal hard disk drives; in fact, they include a normal hard disk drive which is mounted on a disk enclosure. ^[5] Nevertheless, the design of external hard disk drives is more targeted at portability, which can be roughly summarized as cost per gigabyte. In the PC Magazine's top 10 external hard drives chart, the cost per gigabyte value varied between 0.3 to 0.5 USD, approximately.^[6] For the same reason, high capacity external hard disk drives (which weigh more) were for a time less common, although external hard disk drives with more than 500 GB of storage capacity are now commonly manufactured.

Although external hard disk drives are intended to be portable, the data cannot be secured on them due to their insufficient shock protection ^[7] especially compared to digital portable media storage devices such flash memories and memory cards. Nonetheless, external hard disk drives cost less than memory cards or flash memories of the same storage, and are the only portable media storage options available in the size of hundreds of gigabytes.

File system, partition, and operating system

Most external hard drives are compatible with the three major operating systems: Windows, Mac OS (Unix), and Linux. On each of these OSs, you have tools for disk formatting (and maybe journaling), and partitioning. Also, you can install the operating system onto these hard drives, thus gaining the capability to boot into them and run programs or applications on a computer.

These external hard disks are also able to run different file systems, such as Mac OS X Extended (Journaled), FAT, and NTFS. The option of using different operating systems and file systems on different partitions

External hard disks can be partitioned and formatted using 'Disk Management Console' under Windows 2000, XP, and Vista, 'Disk Utility' and 'BootCamp' under Mac OS X or 'Gparted', and 'Qtparted' under Linux.