(1) Two or more systems working together. See clustering.

(2) Also called an "allocation unit" or "file allocation unit," it is some number of disk sectors that are treated as a 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 32KB cluster (see table below), the 1KB file takes up 32KB of disk space. Following are the cluster sizes for the FAT file systems on Windows/DOS computers. See FAT, FAT32 and lost cluster.

                       FAT16
     Disk Size         Cluster size

        0-128MB         2KB
      128-256MB         4KB
      256-512MB         8KB
    512MB-1GB          16KB
        1-2GB          32KB

                       FAT32
    Disk Size          Cluster size

    512MB-8GB           4KB
        8-16GB          8KB
       16-32GB         16KB
       32GB+           32KB