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

48 Chapter2
Disk Layout
The VxFS Version 1 Disk Layout
Figure 2-2 Allocation Unit Structure
One or more allocation units exist per file system. Allocation units are
located immediately after the intent log. The number and size of
allocation units can be specified when the file system is made. All of the
allocation units, except possibly the last one, are of equal size. If space is
limited, the last allocation unit can have a partial set of data blocks to
allow use of all remaining blocks.
Allocation Unit Header
The allocation unit headercontains a copy of the file system’s super-block
that is used to verify that the allocation unit matches the super-block of
the file system. The super-block copies contained in allocation unit
headers can also be used for recovery purposes if the super-block is
corrupted or destroyed. The allocation unit header occupies the first
block of each allocation unit.
Allocation Unit Header
Allocation Unit Summary
Free Inode Map
Extended Inode Operations Map
Free Extent Map
Padding
Inode List
Data Blocks