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For each file, exFAT uses two separate 64-bit fields in the directory: the valid data length (VDL), which indicates the real size of the file, and the physical data length. To provide improvement in the allocation of cluster storage for a new file, Microsoft incorporated a method to pre-allocate contiguous clusters and bypass the use of ...
The limit on partition size was dictated by the 8-bit signed count of sectors per cluster, which originally had a maximum power-of-two value of 64. With the standard hard disk sector size of 512 bytes, this gives a maximum of 32 KB cluster size, thereby fixing the "definitive" limit for the FAT16 partition size at 2 GB for sector size 512.
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.
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, [2] [3] so users of Microsoft Windows have to use NTFS or exFAT instead.
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).
Some researchers have made a functional and experimental analysis of several distributed file systems including HDFS, Ceph, Gluster, Lustre and old (1.6.x) version of MooseFS, although this document is from 2013 and a lot of information are outdated (e.g. MooseFS had no HA for Metadata Server at that time).
exFAT is supported in macOS starting with version 10.6.5 (Snow Leopard). [32] Support in other operating systems is sparse since implementing support for exFAT requires a license. exFAT is the only file system that is fully supported on both macOS and Windows that can hold files larger than 4 GB. [33] [34]
Increasing the size of the drive will proportionately increase the size of the bitmap, while multiplying the sector size will produce a proportionate reduction. When the operating system (OS) needs to write a file, it will scan the bitmap until it finds enough free locations to fit the file. If a 12 KiB file were stored on the example drive ...