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 the mirror snapshot type
Unlike a copy-on-write, a mirror is a complete data copy stored on a separate disk, physically independent of the original. Every change or write to the data on the primary disk is also made to the copy on the secondary disk. The copy is a "mirror" image of the source data.
As in a copy-on-write, transactions are allowed to finish and new I/O on the primary disk is briefly halted. When the mirror image is brought up-to-date with the source, the mirror is split from the primary. After the mirror is split, new changes can be made to the primary but not to the mirror. The mirror can now be backed up (see next diagram).
If the mirror is to be used again it must be brought up-to-date with the primary volume (synchronized). During synchronization, the changes that were made to the primary volume - while the mirror was split - are written to the mirror.
Since mirroring requires a complete copy of the primary on a separate device (same size as the primary), it consumes more disk space than copy-on-write.