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 quiescing the system
Before a useful snapshot can be created, the data to back up must be transactionally consistent or complete. A transaction is a single data action, such as updating a patient's record in a medical database, or creating a record for a new patient. Such a transaction is composed of multiple I/O requests (search, copy, send, write, and so forth). Until the transaction's I/O requests are complete, the data is inconsistent and may be unsuitable for backup.
Transactions affect all levels of the storage management stack (file system, volume manager, and so forth). A transaction generates further transactions as a request is handed off to the next level of the stack. For instance, in the file system, an I/O request from a database application constitutes a transaction and may be split into many disk references. All these disk references must be complete for the original request to be fulfilled. Thus, the creation of the snapshot must be coordinated with any application or process that can affect the transactional consistency of the data.
The means of coordination is called quiesce (literally, to make quiet or place in repose). Quiesce involves pausing the database application or process until the data is transactionally consistent. Applications and the storage management stack must all be quiesced before a useful snapshot can be made.