Veritas File System 5.1 SP1 Administrator"s Guide (5900-1499, April 2011)

The Version 4 file system also moves away from the model of storing AU structural
data at the start of an AU and puts all structural information in files. So expanding
the file system structures simply requires extending the appropriate structural
files. This removes the extent size restriction imposed by the previous layouts.
All Version 4 structural files reside in the structural fileset.
The structural files in the Version 4 disk layout are:
DescriptionFile
Contains the object location table (OLT). The OLT, which is referenced
from the super-block, is used to locate the other structural files.
object location
table file
Encapsulates the super-block and super-block replicas. Although the
location of the primary super-block is known, the label file can be used
to locate super-block copies if there is structural damage to the file
system.
label file
Records device information such as volume length and volume label,
and contains pointers to other structural files.
device file
Holds information on a per-fileset basis. This may include the inode
of the fileset's inode list file, the maximum number of inodes allowed,
an indication of whether the file system supports large files, and the
inode number of the quotas file if the fileset supports quotas. When
a file system is created, there are two filesets—the structural fileset
defines the file system structure, the primary fileset contains user
data.
fileset header file
Both the primary fileset and the structural fileset have their own set
of inodes stored in an inode list file. Only the inodes in the primary
fileset are visible to users. When the number of inodes is increased,
the kernel increases the size of the inode list file.
inode list file
Holds the free inode map, extended operations map, and a summary
of inode resources.
inode allocation
unit file
Maps the block used by the file system intent log.log file
Indicates the allocation state of each AU by defining whether each
AU is free, allocated as a whole (no bitmaps allocated), or expanded,
in which case the bitmaps associated with each AU determine which
extents are allocated.
extent allocation
unit state file
Contains the AU summary for each allocation unit, which contains
the number of free extents of each size. The summary for an extent
is created only when an allocation unit is expanded for use.
extent allocation
unit summary file
Disk layout
VxFS Version 4 disk layout
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