EFS
From Just Solve the File Format Problem
EFS (Extent File System) is a file system formerly used in Silicon Graphics IRIX systems before 5.3, in which version 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.
