Disk Drive

A disk drive is a device that allows a computer to read from and write data to a disk. The most common type of disk drive is a hard disk drive (HDD), and the term disk drive and hard disk drive are typically used interchangeably. Other types include optical drives, storage devices, and floppy drives. A disk drive is commonly found in PCs, servers, laptops, and storage arrays.

Disk drives can either be housed internally within a computer or housed in a separate box that is external to the computer. They work by rotating very rapidly around a head or heads that reads and writes data. Hard disk drives and removable disk drives use a magnetic head, while an optical drive uses a laser. A disk drive differs from a solid state drive (SSD), which has no moving parts and offers greater performance but also costs more and generally offers less capacity.

Parts of a disk drive

A disk drive is made up of many moving parts:

  • Platter: The platter is the actual disk inside the drive that stores the magnetized data. Traditionally, platters are made of a light aluminum alloy and coated with a magnetizable material. Newer technologies use glass and/or ceramic platters because they are thinner and more heat resistant.
  • Spindle/Motor: The platters are attached at the center to a rod or pin called a spindle that is directly attached to the shaft of the motor that controls the speed of rotation.
  • Read/Write Heads: Read/write heads read and write data to the platters. When one head is over a track, all other heads are at the same location over their respective surfaces. The read/write heads convert the electronic 0s and 1s in the magnetic fields on the disks.
  • Head-Actuator Assembly: All heads are attached to a single head actuator, or actuator arm, that moves the heads around the platters.
  • Logic Board: The platters, spindle, spindle motor, head actuator, and the read/write heads are all contained in a chamber called the head disk assembly (HDA). Outside of the HDA is the logic board, which controls the movements of the internal parts and controls the movement of data into and out of the drive.

SSD vs. HDD

Solid state drives have led to a decline in enterprise hard disk use and popularity. An SSD is a high-performance, plug-and-play storage device that requires no moving parts. Solid state drives use flash technology, which consists of small cells that conduct electricity (semiconductors). They are faster, more durable, and more energy-efficient than a hard disk. 

Solid state drives vs. hard disk drives: Cost 

A major drawback of SSDs is their cost. Though prices have decreased over the past decade, they’re still more expensive in dollars per gigabyte than HDDs. While hard disks still exist in cheaper and older systems, SSDs are now used in many mainstream computer systems, such as the MacBook Pro. SDDs are also much faster and will boot in less than a minute, whereas a hard disk takes time to speed up and will almost always boot, launch, and transfer files more slowly. 

 

Solid state drives vs. hard disk drives: Data center suitability

SSDs are often the better choice for data that needs to be quickly accessed (hot data); in data centers, they power critical application data. HDDs, however, are cheaper for cold or archive data, which isn’t used as frequently. Because the data doesn’t need to be rapidly accessed, it’s less expensive to store it on a cheaper drive. 

Although the most common SSD form factor, the M.2, is very popular for computers and servers, it isn’t yet fully optimized for heavy enterprise data center use. SSDs need better cooling to be most effective in data centers. The EDSFF (Enterprise and Data Center Standard Form Factor) drive is an enterprise-focused form factor that is better optimized for large, data-intensive applications because it has better cooling and subsequent power and cost savings. 

Though SSDs are faster for critical applications, many enterprises still use hard drive arrays for their storage systems. Hard disks are still cheaper, especially for high capacity storage, which companies need as the amount of enterprise data increases. 

Disk drive technologies

Hard disk drives and arrays use hardware and software-based systems to back up and protect data from disasters and theft. 

RAID

The most common example of redundancy is RAID (Redundant Array of Independent Disks), a system for disk arrays that uses technology to create copies of data. RAID technologies include: 

  • Striping, which distributes data across multiple disks
  • Parity, a mathematical method for using algorithms to restore data if one disk fails
  • Mirroring, which copies all of the data from one disk onto the one next to it

RAID has different levels, which use different combinations of mirroring, striping, and parity and can tolerate different numbers of disk failure. 

Full disk encryption

Encrypting an entire disk drive prevents people without the decryption key from accessing any of the data on the drive. This differs from file level encryption, which only encrypts individual files. A user must provide the decryption key when they boot the hard drive; otherwise, all the data on the disk is restricted. Full disk encryption is useful for protecting data at rest from attackers and theft. 

Explore full disk encryption vendors: Top 10 Full Disk Encryption Software Products

Self-encrypting drives

Self-encrypting drives keep encryption keys restricted to the disk hardware; they’re inaccessible by software programs. Data is automatically encrypted with the disk’s key. This protects data from attacks that come through computer malware

Disk drive software

Disk data recovery software:

  • TestDisk
  • Recuva

Partition management software:

  • EaseUS Partition Master
  • MiniTool Partition Wizard

Disk use and management

  • WinDirStat
  • Treesize

Disk cloning software:

  • CloneZilla
  • Acronis True Image
  • Macrium Reflect

Disk image software:

  • OSFMount

Disk defragmentation:

  • Defraggler
  • Smart Defrag
  • Auslogics Disk Defrag

Disk erasure software:

  • Darik’s Boot and Nuke (DBAN)

Disk performance management, benchmarking, and diagnostics: 

  • HD Tune
  • CrystalDiskInfo
  • HDDScan

Disk encryption software:

  • VeraCrypt
  • McAfee Complete Data Protection
  • Micro Focus ZENworks Full Disk Encryption

Virtual disk creation software:

  • Disk2vhd

To manage and clean your computer’s internal disk, read How to Clean a Computer’s Hard Drive.

This article was updated Jan 2022 by Jenna Phipps.

Vangie Beal
Vangie Beal
Vangie Beal is a freelance business and technology writer covering Internet technologies and online business since the late '90s.

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