EFS

EFS (Extent File System) is a file system formerly used in Silicon Graphics IRIX systems before 5.3, after which it was replaced with XFS.

In file system terminology, an "extent" is a contiguous block of storage space. EFS uses such blocks to hold files, meaning that files are stored in consecutive blocks of the storage medium instead of scattered around as some other file systems might store them.

Links

 * Some information about its structure
 * Wikipedia article
 * EFS support for Linux
 * EFS support for NetBSD