A file on the disk will ideally be entirely contiguous , i.e. the blocks which contain the file will be sequential .
Disk fragmentation will sometimes require the file to be located in discontiguous clusters in which case the fragments are called ' extents ' .
A file on the disk will ideally be entirely contiguous , i.e. the blocks which contain the file will be sequential , but disk fragmentation will sometimes require the file to be located in discontiguous clusters in which case the fragments are called ' extents ' .