NetBackup™ Snapshot Client Administrator's Guide
- Introduction
- Installation
- Policy configuration
- Selecting the snapshot method
- About using alternate client backup
- Configuring alternate client backup
- Policy configuration tips
- About disabling snapshots
- NAS snapshot configuration
- Dynamic data streaming for D-NAS workloads
- Setting up a NAS-Data-Protection policy
- FlashBackup configuration
- Instant Recovery configuration
- About Instant Recovery
- About sizing the cache for Instant Recovery copy-on-write snapshots
- About storage lifecycle policies for snapshots
- Configuration of software-based snapshot methods
- Support for Cluster Volume Manager Environments (CVM)
- Configuration of snapshot methods for disk arrays
- OS-specific configuration tasks
- About IBM DS6000 and DS8000 arrays
- Configuring NetBackup to access the IBM DS6000 or DS8000 array
- About IBM DS4000 array
- About Hitachi SMS/WMS/AMS, USP/NSC, USP-V/VM
- Hitachi array software requirements
- About HP-XP arrays
- About array troubleshooting
- Notes on Media Server and Third-Party Copy methods
- Backup and restore procedures
- Snapshot management
- Troubleshooting
- Logging directories for UNIX platforms
- Logging folders for Windows platforms
- FlashBackup and status code 13
- Appendix A. Managing nbu_snap (Solaris)
- Appendix B. Overview of snapshot operations
About sizing the cache for Instant Recovery copy-on-write snapshots
A copy-on-write snapshot requires cache space for storing the changes that occur on the source device during the life of the snapshot. While the snapshot is active, any blocks that are about to be changed by user activity are copied to the cache. Blocks that do not change on the source are not copied. Compared to a fully-allocated snapshot (clone or mirror), a copy-on-write snapshot may consume relatively little disk space and can be executed very quickly.
As a rule, the appropriate size for the cache depends on the amount of user activity that occurs during the life of the snapshot. The more changes in the source data, or the longer the life of the snapshot, the more blocks that are likely to be changed. As a result, more data must be stored in the cache.
The size of the file system or raw partition does not determine cache size. If little change activity occurs on the source during the life of the snapshot, little cache space is required, even for a large file system.
Note:
If the cache runs out of space, the snapshot may fail.