Veritas™ File System 5.0.1 Administrator's Guide

Online backup using file

system snapshots

This chapter includes the following topics:

■ About snapshot file systems

■ Snapshot file system backups

■ Creating a snapshot file system

■ Backup examples

■ Snapshot file system performance

■ Differences Between Snapshots and Storage Checkpoints

■ About snapshot file system disk structure

■ How a snapshot file system works

About snapshot file systems

A snapshot file system is an exact image of a VxFS file system, referred to as the

snapped file system, that provides a mechanism for making backups. The snapshot

is a consistent view of the file system “snapped” at the point in time the snapshot

is made. You can select files to back up from the snapshot using a standard utility

such as cpio or cp, or back up the entire file system image using the vxdump or

fscat utilities.

You use the mount command to create a snapshot file system; the mkfs command

is not required. A snapshot file system is always read-only. A snapshot file system

exists only as long as it and the snapped file system are mounted and ceases to

exist when unmounted. A snapped file system cannot be unmounted until all of

Chapter