Storage Hard Drives

Internal Drives

IDE or PATA - IDE hard disks have been around for quite a few years. The term IDE stands for Integrated Drive Electronics and ATA stands for Advanced Technology Attachment. IDE drives are also known as PATA drives. The P stands for parallel, because the data is transferred in parallel down the 40 wires in the ribbon cable. Note that IDE hard disks and optical disc drives have now largely been replaced by serial ATA (SATA) drives.

SATA - Serial Advanced Technology Attachment is a serial link - a single cable with a minimum of four wires creates a point-to-point connection between devices. As an evolution of the older IDE/PATA physical storage interface, SATA host-adapters and devices communicate via a high-speed serial cable. One of the main design advantages of Serial ATA is that the thinner serial cables facilitate more efficient airflow inside a form factor and also allow for smaller chassis designs. In contrast, IDE cables used in parallel ATA systems are bulkier than Serial ATA cables and can only extend to 40cm long, while Serial ATA cables can extend up to one meter.

SCSI - The main difference between SCSI and SATA is that while SCSI has a processor integrated into the controller, SATA makes greater use of the system processor to serve that function. This makes SCSI drives much more expensive and are usually used in servers and workstations were performance is the main objective.

External Drives

USB - The more common USB external drive are the the USB flash drives (aka as USB keys). These consist of a NAND-type flash memory data storage device integrated with a USB interface. USB flash drives are typically removable and rewritable and most USB flash drives weigh less than an ounce (28g). Storage capacities typically range from 64 MB to 128 GB with steady improvements in size and price per gigabyte. Some allow 1 million write or erase cycles and have 10-year data retention. USB flash drives offer potential advantages over other portable storage devices, they have a more compact shape, operate faster, hold much more data, have a more durable design, and operate more reliably due to their lack of moving parts. Actually, nothing actually moves in a flash drive, however the term drive persists because computers read and write flash-drive data using the same system commands as for a mechanical disk drive, with the storage appearing to the computer operating system and user interface as just another drive.

A complete different class of external USB disks drives are standard IDE or SATA drives mounted inside separated cases that can be connect to a computer using the USB port (or in some cases FireWire/IEEE1394 ports). They are available as self-contained packages that include the drive and the case, and separate USB enclosures with mounting hardware and cable connections for loose drives. Unlike smaller USB devices, these full-sized disks drives require separate power connection and adapters.

Network (Ethernet/Wireless) - Network drives are standard drives with a network interface which allows to access remotely to data using any LAN infrastructure (Cabled or Wired Ethernet). These devices allow the data to be shared my multiple users and terminals. Some devices offer simultaneously network and USB interfaces (standard or emulating a network connection through the USB interface).

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