Veritas™ File System 5.0.1 Programmer's Reference Guide

Veritas File System I/O

This chapter includes the following topics:

■ About Veritas File System I/O

■ Freeze and thaw

■ Caching advisories

■ Extents

About Veritas File System I/O

Veritas File System (VxFS) I/O controls the access of data on a VxFS file system.

VxFS APIs are provided for freezing and thawing file systems, administering

caching advisories, and administering extent attributes.

Note: Unlike the other VxFS APIs described in this document, the APIs described

in this chapter are available in previous releases of VxFS on all platforms. The

exception is the API that provides concurrent I/O access through the VxFS caching

advisories, which is available on VxFS 4.1 and later releases.

Freeze and thaw

Freezing a file system temporarily blocks all I/O operations to a file system and

then performs a sync on the file system. Current operations are completed and

the file system is synchronized to disk. Freezing a file system is a necessary step

for obtaining a stable and consistent image of the file system at the volume level.

Consistent volume-level file system images can be obtained and used with a file

system snapshot tool. The freeze operation flushes all buffers and pages in the

Chapter