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

Storage Checkpoints
Types of Storage Checkpoints
Chapter 5 79
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 86)
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 86).
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 93). 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.