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.[1]
History
The first commercial hard disks were large and cumbersome, and were not stored within the computer itself so therefore fits within the definition external hard disk. The hard disk platters are stored within protective covers or memory units, which sits outside. These hard disks were soon evolved to be compact enough that the disks were able to be mounted into bays inside a computer.
By 1980, internal drives became the system of choice for computers running Windows, while external hard drives remained popular for much longer on the Apple Macintosh and other platforms. Every Mac made between 1986 and 1998 has a SCSI port on the back, making external expansion easy; also, "toaster" Macs did not have easily accessible hard drive bays (or, in the case of the Mac Plus, any hard drive bay at all), so on those models, external SCSI disks were the only reasonable option. These external drives, like the Apple ProFile are in no way as portable nor as compact as the modern ones for commercial use.[2] [3] [4]
After the Internet has been introduced, more information and files needs to be stored than ever before, and more back-ups be made due to threats such as viruses. Once again, external hard drives are popular among users of all platforms.[5]
Presently, the market for external hard disks are aimed towards portability, as well as a higher amount of memory. Currently the commercial external hard disks of the highest capicity are usually found at 1 TB or 1.5 TB from manufacturers such as Hitachi, SimpleTech, Western Digital, Seagate, CMS, and LaCie
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. Cite error: A <ref> tag is missing the closing </ref> (see the help page). 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 aimed to be portable, the data cannot be secured on them due to their insufficient shock protection [6] 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 OS's you have tools for disk formatting (and maybe journaling), and partitioning Also, you can install the operating system onto these hard drives and thus gaining the capability to boot into them and running 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' (Windows Vista), 'Disk Utility' or 'BootCamp' (Mac OS X). Users of Windows XP will need to download third party software to such as Acronis True Image or Norton PartitionMagic have these functions on their PC.
Manufacturers of external hard disks/drives
Active manufacturers
These companies still manufacture hard disks and are in the international market. (This list is in no way complete.)
- CMS
- Dell
- Hitachi
- IBM
- Iomega
- LaCie
- Seagate and Maxtor (the latter was acquired by the former in 2006)
- SimpleTech
- Toshiba
- Western Digital
- Philips
Former manufacturers
These manufacturers have manufactured external hard disks, but are currently not doing so
- Apple Inc.
References
- ^ "External hard drive". Electronics Manufacturers. Retrieved 2007-12-29.
- ^ "Five decades of disk drive industry firsts". disktrend. Retrieved 2008-01-10.
- ^ "IBM 3340 direct access storage facility". IBM. Retrieved 2008-01-10.
- ^ "IBM 1301 disk storage unit". IBM. Retrieved 2008-01-10.
- ^ "What is an External Hard Drive?". Wisegeek. Retrieved 2007-01-10.
- ^ "What makes a greate external hard drive" (PDF) (PDF). Retrieved 2007-12-29.