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

Chapter 2 57
Disk Layout
The VxFS Version 2 Disk Layout
one 2048 block extent.
The file system uses this bitmapping scheme to find an available extent
closest in size to the space required. This keeps files as contiguous as
possible for faster performance.
Padding It may be desirable to align data blocks to a physical
boundary. To facilitate this, the system administrator may specify that a
gap be left between the end of the free extent map and the first data
block. See Chapter 6 , “Application Interface,” for additional information
on alignment.
Data Blocks The balance of the allocation unit is occupied by data
blocks. Data blocks contain the actual data stored in files and directories.
Filesets and Structural Files
This section describes the structural elements of the file system that are
not necessarily in fixed locations on the disk.
With the Version 2 layout, many structural elements of the file system
are encapsulated in files to allow dynamic allocation of the file system
structure. Files that store this file system structural data are referred to
as structural files . As the file system grows, more space is allocated
to the structural files. Structural files are intended for file system use
only and are not generally visible to users.
The Version 2 layout supports filesets , which are collections of files
that exist within a file system. In the current release, each file system
contains two filesets:
attribute fileset A special fileset that stores the structural elements of
the file system in the form of structural files. These
files are a property of the file system and are not
normally visible to the user.
primary fileset A fileset that contains files that are visible to and
accessible by users.
Structural files exist in the attribute fileset only and include
thefollowing:
fileset header file A file that contains a series of fileset
headers.
inode list file A file that contains a series of inodes.