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Managing filesystem types

Extent-based allocation on a vxfs filesystem

An extent is defined as one or more adjacent blocks of data within the filesystem. When storage is added to a file on a vxfs filesystem, it is grouped in extents, as opposed to being allocated a block at a time (as is done by the s5, sfs, and ufs filesystems).

Using extents means that disk I/O to and from a file can be done in units of multiple blocks. This type of I/O can occur if storage is allocated in units of consecutive blocks. For sequential I/O, multiple block operations are considerably faster than block-at-a-time operations. Almost all disk drives accept I/O operations of multiple blocks.


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UnixWare 7 Release 7.1.4 - 22 April 2004