Abstract: A combined file allocation table file system (CFAT file system) uses two or more FAT file systems with different cluster sizes to form a single user visible FAT file system to reduce disk fragmentation. The FAT file system having the largest cluster size is used to store all of the other small FAT file systems as files with holes. The clusters of the small FAT file systems thus do not occupy disk space until they are allocated. Files containing user data are stored in one or many of the large and small FAT file systems to achieve optimal storage. More clusters are available for storing files with sizes that are smaller than the size of one large cluster. A CFAT file system includes: a large file allocation table for large clusters, a file allocation table extension to provide holes within the CFAT file system, and any number of small file allocation tables providing a variety of small cluster sizes.

Abstract: A file system includes a file allocation table (FAT) and a file allocation table extension. Each FAT element of the file allocation table corresponds to a unique cluster on disk and represents the status of that cluster. These FAT elements are indexed by a cluster number that corresponds to that cluster on disk. Each element of the file allocation table extension does not correspond to any region on disk. Writing a file divided into clusters to disk first involves determining whether the cluster may be represented by a hole. If not, the cluster is written to disk at a particular cluster number and a status indicator is stored in the file allocation table at a FAT element indexed by that cluster number indicating that the cluster is allocated. If the cluster may be represented by a hole, a status indicator is stored in the file allocation table extension at an element indicating that the cluster is not stored on the disk of the computer.

Abstract: A method, apparatus, and computer-usable medium for compressing data in a file system utilizing the concept of "holes". A mapping table in a file system maps the logical blocks of a file to actual physical blocks on disk where the data is stored. Blocks may be arranged in units of a cluster, and the file may be compressed cluster-by-cluster. Holes are used within a cluster to indicate not only that a cluster has been compressed, but also the compression algorithm used. Different clusters within a file may be compressed with different compression algorithms. A unit of data is compressed, with the result that the file occupies fewer physical blocks than it has logical blocks. The mapping table is updated to indicate that for a given unit of data compressed, fewer physical blocks are needed. Certain logical blocks belonging to this unit of data are not mapped to physical blocks but are mapped to a hole.