HP JFS 3.3 and HP OnLineJFS 3.3 VERITAS File System 3.3 System Administrator's Guide

Chapter 1 25
The VxFS File System
Extent-Based Allocation
for future types.
The current typed format is used on regular files only when indirection is
needed. Typed records are longer than the previous format and require
less direct entries in the inode. Newly created files start out using the old
format which allows for ten direct extents in the inode. The inode's block
map is converted to the typed format when indirection is needed to offer
the advantages of both formats.