VERITAS File System 4.1 Administrator's Guide

Storage Checkpoints
What is Storage Checkpoint ?
Chapter 590
What is Storage Checkpoint ?
VERITAS File System provides a unique Storage Checkpoint facility that quickly creates a
persistent image of a file system at an exact point in time. Storage Checkpoints significantly
reduce I/O overhead by identifying and maintaining only the file system blocks that have
changed since the last Storage Checkpoint or backup through a copy-on-write technique (See
“How a Storage Checkpoint Works” on page 92). Unlike a disk-based mirroring technology
that requires a separate storage space, this VERITAS technology minimizes the use of disk
space by creating a Storage Checkpoint within the same free space available to the file
system.
Storage Checkpoints are data objects that are managed and controlled by the file system. As a
result, Storage Checkpoints are persistent across system reboots and crashes.You can create,
remove, and rename Storage Checkpoints because they are data objects with associated
names(See “Storage Checkpoint Administration” on page 97).After you create a Storage
Checkpoint of a mounted file system, you can also continue to create, remove, and update files
on the file system without affecting the logical image of the Storage Checkpoint. This
technology preserves not only the name space (directory hierarchy) ofthe file system, but also
the user data as it existed at the moment the Storage Checkpoint was taken.
Storage Checkpoints differ from VERITAS File System snapshots in the following ways
because they:
• Allow write operations to the Storage Checkpoint itself.
• Persist after a system reboot or failure.
• Share the same pool of free space as the file system.
• Maintain a relationship with other Storage Checkpoints by identifying changed file blocks
since the last Storage Checkpoint.
• Have multiple, read-only Storage Checkpoints that reduce I/O operations and required
storage space because the most recent Storage Checkpoint is the only one that
accumulates updates from the primary file system.
Various backup and replication solutions can take advantage of Storage Checkpoints. The
ability of Storage Checkpoints to track the file system blocks, which have changed since the
last Storage Checkpoint, facilitates backup and replication applications that need to retrieve
the changed data. Storage Checkpoints significantly minimize data movement and may
promote higher availability and data integrity by increasing the frequency of backup and
replication solutions.