In computer storage, fragmentation is a phenomenon in which storage space is used inefficiently, reducing capacity or performance and often both. The exact consequences of fragmentation depend on the specific system of storage allocation in use and the particular form of fragmentation. In many cases, fragmentation leads to storage space being "wasted", and in that case the term also refers to the wasted space itself. For other systems (e.g. the FAT file system) the space used to store given data (e.g. files) is the same regardless of the degree of fragmentation (from none to extreme).