Types of Computer Hard Disk Drives

Types of Computer Hard Disk Drives

Computers rely on hard disk drives to store data permanently. Hard disk drives (HDDs) are thus storage devices used to store and retrieve digital information that will be required for future reference.

Hard drives are non-volatile meaning that they retain data even when they do not have power. The information stored remains safe and intact unless the hard drive is destroyed or interfered with.

The information is stored or retrieved in a random access manner as opposed to sequential access. This implies that blocks of data can be accessed at any time they are required without going through other data blocks.

Hard Disk Drives Were Introduced in 1956 by IBM

Hard disk drives were introduced in 1956 by IBM, a time when they were being used with general purpose mainframe and minicomputers. Like other electronic devices, these storage devices have witnessed numerous technological changes over the years. This is in terms of capacity, size, shape, internal structure, performance, interface, mode of storing data, among other features.

These numerous changes have made them to be here to stay, ‘so to write’, not like other devices that become obsolete the moment they are introduced in the market.

Computer Hard Drive Types

Currently, we can group the hard drives into four types:-

  • Parallel Advanced Technology Attachment – (PATA)
  • Serial ATA (SATA)
  • Small Computer System Interface (SCSI)
  • Solid State Drives (SSD)

Parallel Advanced Technology Attachment – (PATA)

Parallel Advanced Technology Attachment – (PATA)

These were the first types of hard disk drives and they make use of the Parallel ATA interface standard to connect to the computers. These types of drives are the ones we refer to as the Integrated Drive Electronics (IDE) and Enhanced Integrated Drive Electronics (EIDE) drives.

These PATA drives were introduced by Western Digital back in 1986. The PATA interface provided a common drive interface technology for connecting hard drives and other devices to the computers. Data transfer rate is up 133MB/s and a maximum of 2 devices can be connected on a drive channel. Most of the motherboards have a provision of two channels, thus a total of 4 EIDE devices can be connected internally.

They make use of a 40 or 80 wire ribbon cable transferring multiple bits of data simultaneously in parallel. These drives store data by the use of magnetism. The internal structure is one of mechanically moving parts. They have been superseded by serial ATA.

An EIDE Hard Disk Drive

A hard disk drive (PATA type)
A hard disk drive (PATA type) | Source

Serial ATA (SATA)

These are the hard drives that have replaced the PATA drives in the desktop and laptop computers. The main physical difference between the two is the interface through which they connect to the computer though the mechanism is the same. SATA disk drives have some advantages over the PATA drives:-

  • SATA disk drives transfer data faster than PATA drives using serial signaling technology
  • SATA cables are thinner, more flexible compared to PATA cables
  • They have a 7-pin data connection, with cable limit of 1 meter
  • Disks do not share bandwidth because it is only one disk drive allowed per SATA controller chip on the computer motherboard
  • They consume less power – requires 250 mV of power as opposed to 5V for PATA

SATA Hard Disk Drive Interface

A SATA hard disk drive
A SATA hard disk drive | Source

Small Computer System Interface (SCSI)

These hard disk drives are quite similar to IDE hard drives but they make use of the SCSI (Small Computer System Interface) interface to connect to the computer. SCSI drives can be connected internally or externally. SCSI devices are connected in a SCSI chain which has to be terminated at the end.

SCSI hard drives are:-

  • Faster
  • Reliable
  • Good for 24/7 operations
  • Have a better scalability and flexibility in arrays (RAID)
  • Well adapted for storing and moving large amounts of data

Solid State Drives (SSD)

These drives are the latest drive technologies we have in the market. They are totally different from the other drives in that they do not consist of moving parts. They also do not store data using magnetism rather instead they make use of flash memory technology. They make use of integrated circuits or semiconductor devices to store data permanently – unless erased.

They have some advantages over the other drives:-

  • Faster data access
  • Less susceptible to shock
  • Lower access times and latency
  • Durability
  • Less power usage

Solid State Drive (SSD)

Solid State Drive (SSD)
Solid State Drive (SSD) | Source

Which type of a hard disk drive do you prefer?

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© 2012 Patrick Kamau

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Comments 4 comments

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Patkay 3 years ago from Nairobi, Kenya Author

lucy patrick, thanks for reading and commenting. I am glad you liked it.

lucy patrick 3 years ago

i like your hub. Thank's patkay.

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Patkay 4 years ago from Nairobi, Kenya Author

Thanks njeri p, for reading and commenting. Glad you liked it.

njeri p 4 years ago

best description patkay. useful

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