Veritas NetBackup Snapshot Client Administrator's Guide
- Snapshot Client features
- About snapshot basics
- Off-host backup overview
- Off-host backup methods
- About alternate client backup
- Snapshot Client requirements
- 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
- Software-based snapshot methods
- Cache device requirements
- About VxFS_Checkpoint
- About VxVM
- About FlashSnap
- About VVR
- About VSS
- 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
- Troubleshooting issues pertaining to all arrays
- Troubleshooting IBM DS6000 and DS8000 arrays
- Troubleshooting IBM4000 arrays
- Troubleshooting Hitachi arrays
- Notes on Media Server and Third-Party Copy methods
- Backup and restore procedures
- About restores from a FlashBackup backup
- Instant Recovery restore features
- About Instant Recovery: block-level restore
- About Instant Recovery: file promotion
- About Instant Recovery: Fast File Resync (Windows clients only)
- About Instant Recovery: point in time rollback
- About configurations for restore
- About restoring from a disk snapshot
- 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
Determining a size for the cache partition
The required size for the cache partition depends on user write activity during the backup, not on the size of the client's file system. If the backup occurs when user activity is heavy, a larger cache is required.
To determine a size for the cache partition
- Consider the period in which the backup is scheduled to occur: the more user activity that is expected, the larger the cache required.
You should execute the following procedure at an appropriate period, when your snapshot backups typically run. If user activity at your site is known to vary with the time of day, a different time could bring very different results.
- Make sure that a raw partition is available on a separate disk.
- During the appropriate backup period, create an nbu_snap snapshot by entering the following as root:
/usr/openv/netbackup/bin/driver/snapon snapshot_source cache
where snapshot_source is the partition on which the client's file system is mounted, and cache is the raw partition to be used as copy-on-write cache. For example:
/usr/openv/netbackup/bin/driver/snapon /omo_cat3 /dev/vx/rdsk/zeb/cache
matched /omo_cat3 to mnttab entry /omo_cat3 mount device: /dev/vx/dsk/omo/vol03 fstype: vxfs snapshot 29 enabled on /omo_cat3 at 06/05/03 15:16:02
- In /usr/openv/netbackup/bin/driver, enter the snaplist and snapcachelist commands.
snaplist shows the following:
Id of each snapshot
Size of the partition containing the client file system
Amount of file system write activity in 512-byte blocks that occurred during the nbu_snap snapshot (under the cached column).
The more blocks that are cached as a result of user activity, the larger the cache partition required.
snapcachelist shows each cache device in use and what percentage has been used (busy). For each cache device that is listed, busy shows the total space that is used in the cache. This value indicates the size of the raw partition that may be required for nbu_snap cache.
More details are available on the snap commands.
See nbu_snap commands.
The snap commands can be used in a script.
If the cache partition is not large enough, the backup fails with status code 13, "file read failed." The /var/adm/messages log may contain errors such as the following:
Mar 24 01:35:58 bison unix: WARNING: sn_alloccache: cache /dev/rdsk/c0t2d0s3 full - all snaps using this cache are now unusable
Using the information that snaplist and snapcachelist provide, you have several options:
Specify a larger (or smaller) partition as cache, depending on the results from snaplist and snapcachelist.
Reschedule backups to a period when less user activity is expected.
If multiple backups use the same cache, reduce the number of concurrent backups by rescheduling some of them.
- When you are finished with the snapshot, you can remove it by entering the following:
where snapid is the numeric id of the snapshot that was created earlier.
NetBackup policies do not control any snapshots that you create manually with the snapon command. When snapon is run manually, it creates a copy-on-write snapshot only. The snapshot remains on the client until it is removed by entering snapoff or the client is restarted.