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Because file size references are stored in eight instead of four bytes, the file size limit has increased to 16 exabytes (EB) (2 64 − 1 bytes, or about 10 19 bytes, which is otherwise limited by a maximum volume size of 128 PB, [nb 2] or 2 57 − 1 bytes), raised from 4 GB (2 32 − 1 bytes) in a standard FAT32 file system. [1]
There are several variants of the FAT file system (e.g. FAT12, FAT16 and FAT32). FAT16 refers to both the original group of FAT file systems with 16-bit wide cluster entries and also to later variants. "VFAT" is an optional extension for long file names, which can work on top of any FAT file system. Volumes using VFAT long-filenames can be read ...
Cluster sizes vary depending on the type of FAT file system being used and the size of the drive; typical cluster sizes range from 2 to 32 KiB. [39] Each file may occupy one or more clusters depending on its size. Thus, a file is represented by a chain of clusters (referred to as a singly linked list).
While storage devices usually have their size expressed in powers of 10 (for instance a 1 TB Solid State Drive will contain at least 1,000,000,000,000 (10 12, 1000 4) bytes), filesystem limits are invariably powers of 2, so usually expressed with IEC prefixes.
The change to 64-bit file sizes frequently required incompatible changes to file system layout, which meant that large-file support sometimes necessitated a file system change. For example, the FAT32 file system does not support files larger than 4 GiB−1 (with older applications even only 2 GiB−1); the variant FAT32+ does support larger ...
FAT32 supports files up to 4 GB. FAT32 is the factory format of larger USB drives and all SDHC cards that are 4 GB or larger. exFAT supports files up to 127 PB. exFAT is the factory format of all SDXC cards, but is incompatible with most flavors of UNIX due to licensing problems. NTFS supports files up to 16 TB.
Windows 7 also supports the newer exFAT file system. As the ReadyBoost cache is stored as a file, the flash drive must be formatted as FAT32, NTFS, or exFAT in order to have a cache size greater than FAT16's 2 GB filesize limit; if the desired cache size is 4 GB (the FAT32 filesize limit) or larger, the drive must be formatted as NTFS or exFAT.
A FAT12 and FAT16 (and FAT32) extension to support database-like file types random file, direct file, keyed file and sequential file in Digital Research FlexOS, IBM 4680 OS and Toshiba 4690 OS. [18] The record size is stored on a file-by-file basis in special entries in the directory table. [19]