VERITAS File System 3.5 (HP OnlineJFS/JFS 3.5) Administrator's Guide (August 2003)

Chapter 1
The VERITAS File System
Disk Layouts
17
Disk Layouts
The disk layout is the way file system information is stored on disk. On VxFS, five disk layout versions,
numbered 1 through 5, were created to support various new features and specific UNIX environments.
Currently, only Version 4 or Version 5 disk layouts can be created, but file systems with Version 2 and
Version 3 disk layouts can be mounted.
See “Disk Layout” on page 121 for a description of the disk layouts.
File System Performance Enhancements
Traditional file systems employ block based allocation schemes that provide adequate random access and
latency for small files, but which limit throughput for larger files. As a result, they are less than optimal
for commercial environments.
VxFS addresses this file system performance issue through an alternative allocation method and
increased user control over allocation, I/O, and caching policies. An overview of the VxFS allocation
policy is provided in the section
“Extent Based Allocation” on page 19.
VxFS provides the following performance enhancements:
• Extent based allocation
• Enhanced mount options
• Data synchronous I/O
• Direct I/O and discovered direct I/O
• Caching advisories
• Enhanced directory features
• Explicit file alignment, extent size, and preallocation controls
• Tunable I/O parameters
• Tunable indirect data extent size
• Integration with VERITAS Volume Manager™ (VxVM®)
• Support for improved database performance
The rest of this chapter, as well as “VxFS Performance: Creating, Mounting, and Tuning File Systems” on
page 29 and “Application Interface” on page 55 provide details on many of these features.