Hard Drive Glossary
Storage and data recovery terms explained in plain English.
A
- Access
- The action of obtaining data from, or writing data to, a data storage device.
- ANSI
- American National Standards Institute — the organisation that publishes many of the standards used by storage devices.
- ATA
- Advanced Technology Attachment. Originally the standard for fixed disk storage in IBM AT-compatible PCs; it became the dominant hard drive interface.
B
- Bad Sector
- An area of a disk that can no longer be read or written reliably. A growing number of bad sectors is an early warning of drive failure.
- Bit
- Short for binary digit. A bit holds a value of 1 or 0 and is the basic unit of data in digital computers.
- Buffer
- A storage area used to temporarily hold data so that differences in transfer or processing speed between sender and receiver can be balanced.
- Byte
- A unit of data made up of eight bits.
C
- Cache
- Fast memory (DRAM) on the drive that temporarily stores recently accessed data or data waiting to be written to the disk.
- Capacity
- The amount of data a storage device can hold, usually expressed in bytes (GB or TB).
- Channel
- A collection of electronic circuits used for writing data to and reading data from the media.
- Clean Room
- A controlled environment with filtered air and very few dust particles, required when a hard drive must be opened for repair.
- Controller
- The chip that manages how data is stored and retrieved — on SSDs it handles the memory chips, wear-levelling and error correction.
D
- Data
- An ordered collection of information.
F
- File System
- The method an operating system uses to organise files on a drive, such as NTFS, FAT32, exFAT, APFS, HFS+ or EXT4.
- Firmware
- Software stored on the drive itself that controls how it operates. Corrupted firmware can make a drive show the wrong name or capacity, or stop responding.
G
- Gigabyte (GB)
- A unit of storage. 1 GB is 1,000,000,000 bytes (decimal) or 1,073,741,824 bytes (binary). Manufacturers use decimal while operating systems use binary — which is why a drive appears smaller in Windows than on the box.
H
- Head Crash
- When a read/write head touches the spinning platter surface, scratching it. Often accompanied by clicking or grinding noises.
I
- Imaging (Cloning)
- Creating a complete sector-by-sector copy of a drive. Professional recovery is always done from the image, not the damaged original.
J
- Jumper
- A small connector used on older drives to set attributes such as Master/Slave — essentially a simple on/off switch.
L
- Latency
- The delay between requesting data and receiving a response. Lower latency is better.
M
- Megabyte (MB)
- A unit of storage: 1 MB is 1,000,000 bytes (decimal) or 1,048,576 bytes (binary).
N
- NAS
- Network Attached Storage — a storage device connected to a network, usually containing several drives in a RAID configuration.
- NVMe
- Non-Volatile Memory Express — a fast interface used by modern M.2 SSDs that connects directly over PCIe.
P
- Partition
- A section of a drive that the operating system treats as a separate volume (for example C: and D:).
- PATA / IDE / EIDE
- Parallel ATA, also called IDE or EIDE — the older hard drive interface that uses a wide parallel ribbon cable. Common versions are ATA-100 and ATA-133 (100 and 133 MB/s).
- PCB
- Printed Circuit Board — the electronics board on the drive. Modern PCBs hold drive-specific data, so a replacement board from another drive rarely works directly.
- Platter
- The rigid, magnetically coated disk inside a hard drive on which data is stored. A drive may contain one or several platters.
R
- RAID
- Redundant Array of Independent Disks — a way of combining several drives so the operating system sees them as one. RAID 0 (striping) offers speed but no fault tolerance; RAID 1 (mirroring) duplicates data; RAID 5 and 6 use parity; RAID 10 combines striping and mirroring.
- RAW Drive
- A drive whose file system cannot be recognised by the operating system, so Windows asks you to format it. Do not format — the data can often be recovered.
- Read
- The action of accessing a storage location and obtaining the stored data.
- Read/Write Head
- The tiny component that flies just above the platter surface to read and write data. Head failure is a common cause of clicking drives.
S
- S.M.A.R.T.
- Self-Monitoring, Analysis and Reporting Technology — built-in drive health monitoring that can warn of upcoming failure.
- SAN
- Storage Area Network — a dedicated high-speed network that provides block-level storage to servers.
- SATA
- Serial ATA — the standard interface that replaced PATA, with thinner cables and higher speeds (1.5, 3 and 6 Gb/s).
- SCSI / SAS
- Small Computer System Interface and its successor Serial Attached SCSI — interfaces used mostly in servers and enterprise storage.
- Spindle Motor
- The motor that spins the platters. A seized motor can stop a drive from spinning up at all.
- SSD
- Solid State Drive — storage that uses flash memory chips instead of spinning platters. Faster and silent, but often fails without warning.
T
- TRIM
- A command that lets the operating system tell an SSD which data blocks are no longer needed, so they can be erased. It is why deleted data on SSDs disappears quickly.
W
- Write
- The action of recording data on a storage device.
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