ACRONIS DD10DB Datasheet download pdf (Page 117)

Hard Disk And File Systems

117

A.9.2 FAT16

The FAT16 file system is widely used by DOS (DR-DOS, MS-DOS, PC-DOS, etc.), Windows

95/98/Me, Windows NT/2000/XP operating systems and is supported by most other

systems.

Main features of FAT16 are the file allocation table (FAT) and clusters. The FAT is the core

of the file system. To increase data safety, it is possible to have several instances of the

FAT (there are usually two of them). A cluster is a minimum data storage unit in the

FAT16 file system. One cluster contains a fixed number (some power of 2) of sectors. The

FAT stores information about what clusters are free, what clusters are bad, and also

defines in what clusters files are stored.

Maximum size of a FAT16 file system is 4 Gigabytes, and the maximum number of

clusters is 65,525, the largest cluster being 128 sectors. Usually the smallest possible

cluster size is selected so that the resulting number of clusters is less than 65,526. The

larger the partition size, the larger the cluster has to be. Most operating systems

incorrectly perform with 128-sector clusters, thus reducing the maximum FAT16 partition

size to 2 Gigabytes.

Usually the larger the cluster size, the more disk space is wasted.

Table 3. The following table gives the approximate dependence of these

losses versus the cluster size:

Cluster Size

Waste

Partition Size

<127 MB 2 KB 2%

128–255 MB 4 KB 4%

256–511 MB 8 KB 10%

512–1023 MB 16 KB 25%

1024–2047 MB 32 KB 40%

2048–4096 MB 64 KB 50%

Like many others, the FAT16 file system has a root folder. Unlike others however, its root

folder is stored in a special place and is limited in size (standard formatting produces a

512-item root folder).

Initially, FAT16 had limitations to file names that could only be eight characters long, plus

a dot, plus three characters of name extension. However, long name support in Windows

95 and Windows NT bypasses this limitation.

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ACRONIS DD10DB Datasheet Page 117