An extension file system (EFS) manages files and memory on a hard drive using contiguous areas of memory called extents, allowing larger files to be stored in a single location and reducing fragmentation. This can increase speed and extend the life of storage hardware. EFS was originally used in the Unix-like operating system IRIX.
An extension file system (EFS) is a method of managing files and memory on a computer hard drive or other physical storage device that uses a series of contiguous areas of memory to store information instead of using known smaller, scattered units like blocks. Some file systems allocate required space for files in small units known as blocks, which can lead to a single medium-length file being physically dispersed across a disk, reducing the speed and efficiency of reading from that file. In the case of an extent file system, all the smaller blocks are tied together in a larger structure known as an extent, meaning that larger files can be stored in a single contiguous location on the physical disk, increasing speed of the drive when reading from that file. While many operating systems support the use of extensions, the term originally applied to the specific initial extension file system of the now discontinued Unix-like operating system known as IRIX®, developed by Silicon Graphics®.
The individual bits and bytes on a physical disk, such as a hard drive or compact disc (CD), are divided into groups based on hardware, operating system, and file system. These are known as logical groupings, because they don’t necessarily have physical boundaries, just those imposed by the system. For several file systems, the logical grouping known as blocks is used as the basic amount of space that can be allocated to store a file. A block can be set to any size, but is usually very small, sometimes consisting of as little as 128 bytes of space.
An extent file system groups blocks on a disk if they are contiguous, meaning they are all physically next to each other on a disk. This collection of blocks is known as an extension. In an extent file system, when a file is written to a physical disk, an extent is allocated instead of individual blocks. The advantage of using extents instead of blocks is that large files require less overhead to create and maintain, and the risk of fragmentation is greatly reduced, though not necessarily eliminated.
File fragmentation occurs when a file requires more space than any available block or extent can provide, meaning that the file must be split up and occupy two or more physically different spaces on a disk. With small blocks, large files can occupy hundreds or thousands of blocks on an entire disk, reducing file access speed. An extent file system allows a large file to be split into different extents, known as indirect extents, although the number of extents required is usually less than if the file were allocated using smaller blocks.
In addition to reducing the amount of overhead required for large files, since information about a single extent must be stored in the file system rather than multiple pointers to different blocks, using extents can also extend the life of some storage hardware. This can occur because contiguous files require less movement from the disk drive’s read head mechanism to access the information. An extension file system also allows for the creation of individual files that can be terabytes or more in length, because, in some cases, an extension can theoretically occupy all available physical space without the need to create large tables or other management overhead .
Protect your devices with Threat Protection by NordVPN
