Veritas NetBackup™ Snapshot Client Administrator's Guide
- Introduction
- Snapshot Client features
- About snapshot basics
- Off-host backup overview
- Off-host backup methods
- Snapshot Client requirements
- Installation
- Policy configuration
- Selecting the snapshot method
- Configuration parameters for Snapshot Client
- About using alternate client backup
- Configuring alternate client backup
- Policy configuration tips
- About disabling snapshots
- FlashBackup configuration
- Instant Recovery configuration
- About Instant Recovery
- About sizing the cache for Instant Recovery copy-on-write snapshots
- About configuring VxVM
- About storage lifecycle policies for snapshots
- Network Attached Storage (NAS) snapshot configuration
- Configuration of software-based snapshot methods
- Support for Cluster Volume Manager Environments (CVM)
- Configuration of snapshot methods for disk arrays
- About the new disk array snapshot methods
- Disk array configuration tasks
- OS-specific configuration tasks
- About VSS configuration (Windows)
- About EMC CLARiiON arrays
- Configuring NetBackup to access the CLARiiON array
- Configuring a NetBackup policy for a CLARiiON array method
- About EMC Symmetrix arrays
- About configuration for EMC_TimeFinder_Mirror
- About configuration for EMC_TimeFinder_Clone
- About HP EVA arrays
- Verifying connectivity from clients to array using SSSU 5.0
- 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
- About restores from a FlashBackup backup
- Instant Recovery restore features
- About configurations for restore
- About restoring from a disk snapshot
- 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
- Appendix C. NetBackup integration with CloudPoint for snapshot managment
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.