There is a potential for data loss in certain NetBackup 7.5 Replication Director configurations when using NetApp SnapVault with the NetApp Plugin 1.0 for Symantec NetBackup.

Article:TECH200752  |  Created: 2012-12-11  |  Updated: 2013-01-22  |  Article URL http://www.symantec.com/docs/TECH200752
Article Type
Technical Solution


Subject

Issue



With NetBackup version 7.5.0.x Replication Director installations, data loss may occur when using SnapVault in Storage Lifecycle Policies (SLPs) to manage Standard backup policies which include multiple NetApp volumes as backup selections.


Error



No error messages will be displayed - this issue will only be discovered when attempts to restore fail.


Environment



This issue affects NetBackup Replication Director 7.5 and above when version NetApp Plugin 1.0 is in use and all of the below conditions are met:

  1. Backup policy type is Standard (in other words, UNIX and Linux clients only)
  2. Multiple volumes are selected as backup selections within a single policy
  3. The Storage Lifecycle Policy includes a SnapVault replication step.
     

Affected copies include all of the SnapVault replicated copies (in all scenarios) and any SnapMirror replicated copies or tar-formatted backups which are descendants of a SnapVault replicated copy (for instance, in a Primary → SnapVault → SnapMirror topology, both the SnapVault replicated copy AND SnapMirror replicated copy would be affected).

A data loss condition can result when the primary copy is expired, leaving only affected copy/copies available for restores.

Note: MS-Windows and NDMP backup policies which meet conditions 2 and 3 as described above may also be affected by this issue; however, there is no data loss condition and a workaround is available.  (For more information, please refer to the Solution below.)


Cause



This issue occurs when snapshots for multiple volumes in the policy get created within the same second (i.e. have the same timestamp).

Consider a policy where snapshots for volumes V1 and V2 are created in the same second.  The following effects may be observed:

  • Restore: During a restore attempt from the affected copy, it may be possible that the contents of V1 are restored to V2.
  • Tape backup: During tape backup from the affected copy, it may be possible that the contents of V1 would also be backed up on the tape for V2's backup.
  • Indexing: During indexing from the affected copy, it is possible that the contents of V1 would also be included in the index of V2.  When this happens, attempt of an Operational Restore will show incorrect data for the volume.

 


Solution



The formal resolution for this issue is included in the following release:

  • NetApp Plugin 1.0P1 for Symantec NetBackup 

To obtain NetApp Plugin 1.0P1, please visit the NetApp support site:
Linux: http://support.netapp.com/NOW/download/software/nbu_plugin_lin/1.0P1/
Windows: http://support.netapp.com/NOW/download/software/nbu_plugin_win/1.0P1/

Please note that upgrading to the recommended version of the NetApp Plug-in will remedy all recoveries from affected SnapVault and SnapMirror copies. However, it will not be possible to remedy the affected tar copies and all affected tar copies need to be expired and fresh backups need to be taken. Upgrading to the NetApp Plug-in 1.0P1 version will also prevent future occurrences of this issue.

Follow these steps after upgrading the plugin:

  • Restore: Redo the restore after upgrading.  Affected SnapVault and SnapMirror copies may be restored safely after upgrade to NetApp Plugin 1.0P1.  Before redoing the restore, any currently mounted incorrect exports will need to be removed from the NetBackup hosts.  NetBackup periodically checks for inactive snapshot mounts and removes those exports. (NetBackup will recreate those exports when the snapshot is required to be accessed again, e.g. for a restore).  The frequency at which NetBackup checks for inactive mounts is dictated by the Image Cleanup Interval setting (NetBackup Administration Console: Host Properties > Master Server > Cleanup).  It may be necessary to wait for a period of time longer than the image cleanup interval after the last restore on that copy.
  • tar backup: After upgrading to NetApp Plugin 1.0P1, run new full backups on affected policies.  Expire any affected tar-formatted backup copies.
  • Indexing: Do not use Operational Restore on affected images.  Instead, after upgrading to NetApp Plugin 1.0P1, use the BAR GUI live browse for restores.

Note:
For any MS-Windows and NDMP backup policies in use which are affected as described above: restore, tape backup, and indexing operations will fail, but upgrading to NetApp Plugin 1.0P1 automatically resolves these failures.  An upgrade of the plugin should be executed as a workaround.

Best Practices:
Symantec strongly recommends the following best practices:
1. Always perform a full DR backup prior to making any changes to your environment.
2. Always make sure that your environment is running the latest version and patch level.
3. Perform periodic "test" restores.
4. Subscribe to technical articles.

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Supplemental Materials

SourceETrack
Value3017578
Description

[BURT657628]CreateExport fails for secondary snaps when there is more than 1 Backup selection members



Article URL http://www.symantec.com/docs/TECH200752


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