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

Chapter 1

The VERITAS File System

Access Control Lists

An Access Control List (ACL) stores a series of entries that identify specific users or groups and their access

privileges for a directory or file. A file may have its own ACL or may share an ACL with other files. ACLs have

the advantage of specifying detailed access permissions for multiple users and groups. Refer to the getacl (1)

and setacl (1) manual pages for information on viewing and setting ACLs. ACLs are supported on cluster file

systems.

Storage Checkpoints

To increase availability, recoverability, and performance, the VERITAS File System offers on-disk and online

backup and restore capabilities that facilitate frequent and efficient backup strategies. Backup and restore

applications can leverage the VERITAS Storage Checkpoint, a disk and I/O efficient copying technology for

creating periodic frozen images of a file system. Storage Checkpoints present a view of a file system at a point

in time, and subsequently identifies and maintains only changed file system blocks. Instead of using a

disk-based mirroring method, Storage Checkpoints save disk space and significantly reduce I/O overhead by

using the free space pool available to a file system.

See “Storage Checkpoints” on page 51 for information on using the Storage Checkpoint feature.

Online Backup

VxFS provides online data backup using the snapshot feature. An image of a mounted file system instantly

becomes an exact read-only copy of the file system at a specific point in time. The original file system is called

the snapped file system, the copy is called the snapshot.

When changes are made to the snapped file system, the old data is copied to the snapshot. When the snapshot

is read, data that has not changed is read from the snapped file system, changed data is read from the

snapshot.

Backups require one of the following methods:

• Copying selected files from the snapshot file system (using find and cpio)

• Backing up the entire file system (using fscat)

• Initiating a full or incremental backup (using vxdump)

See “Online Backup” on page 65 for information on doing backups using the snapshot feature.