Veritas File System 4.1 Administrator's Guide (HP-UX 11i v3, February 2007)

Online Backup Using File System Snapshots
Differences Between Snapshots and Storage Checkpoints
Chapter 6 107
Differences Between Snapshots and Storage Checkpoints
While snapshots and Storage Checkpoints both create a point-in-time image of a file system and only the
changed data blocks are updated, there are significant differences between the two technologies:
• Snapshots require a separate device for storage. Storage Checkpoints reside on the same device as the
original file system.
• Snapshots are read-only. Storage Checkpoints can be read-only or read-write.
• Snapshots are transient. Storage Checkpoints are persistent.
• Snapshots cease to exist after being unmounted. Storage Checkpoints can exist and be mounted on their
own.
• Snapshots track changed blocks on the file system level. Storage Checkpoints track changed blocks on
each file in the file system.
• Although there can be more than one snapshot of a file system, they are all based on a single, parent file
system. Storage Checkpoints can be based on other Storage Checkpoints.
Storage Checkpoints also serve as the enabling technology for two other VERITAS features: Block-Level
Incremental Backups and Storage Rollback, which are used extensively for backing up databases. See
Chapter 5, “Storage Checkpoints,” on page 73 for more information.