(1) Multiple systems or devices working together. See
clustering.
(2) A group of sectors in a storage drive that are treated as a single unit. Also called an "allocation unit" or "file allocation unit," a cluster is the smallest unit of storage the operating system's file system can manage. That means if a 1KB file is stored in a system with a 4KB cluster (see table below), the 1KB file takes up 4KB of disk space.
Following are the cluster sizes for the various Windows file systems starting with Windows XP. When FAT32 came out, the reduction of cluster sizes from 16KB and 32KB down to 4KB saved a lot of space for small files. See
file system,
FAT,
FAT32 and
lost cluster.
Cluster Size
Drive FAT16 FAT32
Size (1984) (1996)
8-32MB 512 bytes --
32-64MB 1KB 512 bytes
64-128MB 2KB 1KB
128-256MB 4KB 2KB
256-512MB 8KB --
512MB-1GB 16KB --
1-2GB 32KB --
2-4GB 64KB --
256MB-8GB -- 4KB
8-16GB -- 8KB
16-32GB -- 16KB
NTFS
(1993)
7-512MB 4KB
512MB-1GB 4KB
1GB-2GB 4KB
2GB-2TB 4KB
2TB-16TB 4KB
16TB-32TB 8KB
32TB-64TB 16KB
64TB-128TB 32KB
128TB-256TB 64KB