VERITAS File SystemÖ 3.5 (HP OnlineJFS/JFS3.5) AdministratorÆs Guide (December 2002)

Chapter 1

The VERITAS File System

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 disk layouts can be created, but file systems with Version 2 and Version 3 disk

layouts can be mounted.

See Appendix C, “Disk Layout,” on page 143 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 5.

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 17 and “Application Interface” on page 43 provide details on many of these features.