Cluster

In regard to computer storage, a cluster is described as the logical unit of file storage on a hard drive. Files stored on a hard drive can take up one or more clusters of storage space. Clusters may be scattered throughout many different locations. A hard drive or hard disk’s FAT (file allocation table) keeps track of all clusters associated with a file. Being that a cluster is viewed as logical unit rather than a physical unit, it’s size may be varied. The maximum amount of clusters on a hard drive all depends on the size of an FAT table entry. Starting with DOS version 4.0, all FAT entries were 16-bits in length. This made way for a maximum amount of 65,536 clusters. A 32-bit FAT entry was supported with Windows 95 OSR2. This allowed an entry to support more clusters and as many as two terabytes of data depending on the size of the hard drive.