VERITAS File System 4.1 Administrator's Guide

The VERITAS File System
Disk Layouts
Chapter 1 15
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 251 for a description of the disk layouts.
File System Performance Enhancements
Traditional file systems employ block based allocation schemes. This provides adequate
random access and latency for small files, but limits 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 18.
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