VERITAS File System 4.1 Administrator's Guide

Storage Checkpoints
Types of Storage Checkpoints
Chapter 5 95
Types of Storage Checkpoints
You can create the following types of Storage Checkpoints:
• Data Storage Checkpoints
• Nodata Storage Checkpoints
• Removable Storage Checkpoints
• Non-mountable Storage Checkpoints
Data Storage Checkpoints
A data Storage Checkpoint is a complete image of the file system at the time the Storage
Checkpoint is created. This type of Storage Checkpoint contains the file system metadata and
file data blocks. You can mount, access, and write to a data Storage Checkpoint just as you
would to a file system. Data Storage Checkpoints are useful for backup applications that
require a consistent and stable image of an active file system. Data Storage Checkpoints
introduce some overhead to the system and to the application performing the write operation.
For best results, limit the life of data Storage Checkpoints to minimize the impact on system
resources. (See “Difference Between a Data and a Nodata Storage Checkpoint” on page 102)
Nodata Storage Checkpoints
A nodata Storage Checkpoint only contains file system metadata-no file data blocks. As the
original file system changes, the nodata Storage Checkpoint records the location of every
changed block. Nodata Storage Checkpoints use minimal system resources and have little
impact on the performance of the file system because the data itself does not have to be
copied. See(“Difference Between a Data and a Nodata Storage Checkpoint” on page 102).
Removable Storage Checkpoints
A removable Storage Checkpoint can "self-destruct" under certain conditions when Data
Storage Checkpoints the file system runs out of space (See “Space Management
Considerations” on page 109). After encountering certain out-of-space (ENOSPC) conditions,
the kernel removes Storage Checkpoints to free up space for the application to continue
running on the file system. In almost all situations, you should create Storage Checkpoints
with the removable attribute.