• Home

DataMole
Data Recovery Resource

Data Recovery Glossary

Clusters
The smallest unit of disk space that can be allocated to a file, clusters are contiguous blocks of sectors on a disk. The cluster size is determined by the operating system.

Defragmentation
The process of optimising read performance by rearranging the clusters on a disk so that files are stored contiguously.

FAT (file allocation table)
The FAT is a table of all the clusters on a disk, used to keep track of which clusters are assigned to which files, and which clusters are free. An entry in the FAT for an occupied cluster tells the operating system where to find the next cluster in the file 'chain'.

Fragmentation
Files are stored as chains of clusters, and the data that is contained within a file can be stored non-contiguously on a disk, or 'fragmented'.

HFS (hierarchical file system)/HFS+
The Mac OS Extended Format (HFS Plus) is a more recent version of the Mac's native file system that increases disk space by using smaller allocation blocks.

MBR (master boot record)
The MBR is a small program stored on the first sector of a disk, which is executed when the computer starts up. The program determines from the partition table which partition to use for booting, and then transfers program control to the boot sector of that partition.

NTFS (new technology file system)
NTFS was introduced when Microsoft released the Windows NT operating system and improves upon FAT, providing a flexible, adaptable, secure and reliable file system for enterprise use.

Platters
The metal disks inside a hard drive that store digital data on a magnetic coating. Hard disks typically contain up to a dozen platters, which are mostly made of an aluminium alloy.

Read/write heads
A head writes to the disk when an electrical current is passed through it, re-aligning the magnetic particles on the media. Conversely, the head produces an electrical current as it passes over the media, thus 'sensing' the data.

Sectors
This is the smallest unit of space on a hard disk, normally containing 512 bytes of data. Sectors are not normally addressed directly by most file systems on hard disks.