Large-file support

Large-file support (LFS) is the term frequently applied to the ability to create files larger than either 2 or 4 GiB on 32-bit s. Traditionally, many operating systems and their underlying implementations used 32-bit integers to represent sizes and positions. Consequently, no file could be larger than 232 − 1 bytes (4 GiB − 1). In many implementations, the problem was exacerbated by treating the sizes as signed numbers, which further lowered the limit to 231 − 1 bytes (2 GiB − 1). Files that were too large for 32-bit operating systems to handle came to be known as large files. While the limit was quite acceptable at a time when hard disks were smaller, the general increase in storage capacity combined with increased server and desktop file usage, especially for database and multimedia files, led to intense pressure for OS vendors to overcome the limitation. In 1996, multiple vendors responded by forming an industry initiative known as the Large File Summit to support large files on POSIX (at the time Windows NT already supported large files on NTFS), an obvious backronym of "LFS". The summit was tasked to define a standardized way to switch to 64-bit numbers to represent file sizes. This switch caused deployment issues and required design modifications, the consequences of which can still be seen: 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 files (up to 256 GiB−1), but (so far) is only supported in some versions of DR-DOS, so users of Microsoft Windows have to use NTFS or exFAT instead. To support binary compatibility with old applications, operating system interfaces had to retain their use of 32-bit file sizes and new interfaces had to be designed specifically for large-file support.