Disk Staging Storage Unit (DSSU) cleanup behavior is different in NetBackup 6.5 in comparison with prior versions.

Article:TECH66149  |  Created: 2008-01-18  |  Updated: 2010-01-23  |  Article URL http://www.symantec.com/docs/TECH66149
Article Type
Technical Solution

Product(s)

Environment

Issue



Disk Staging Storage Unit (DSSU) cleanup behavior is different in NetBackup 6.5 in comparison with prior versions.

Solution



It is important to understand that NetBackup 6.5 staging and high water mark processing is very different from 5.x and 6.0.

In NetBackup 5.x and 6.0, High Water Mark value does not apply to disk staging storage units. The only condition that triggered staged (but not expired) image cleanup was the disk full condition reached during a backup. If this was encountered, all disk backups to that media server (not only to that storage unit) were temporarily paused and a cleanup process was launched to clean the oldest 10 images that had been staged. This would not necessarily mean that it would hit the Low Water Mark as a result. Backups were then resumed until the disk full condition was encountered again, and then the process would repeat.

In essence, staged images were cleaned up in a reactive manner in NetBackup prior to 6.5.

Since NetBackup 6.5, images are cleaned up in a proactive manner and the process is quite different. Whenever a DSSU is above its high water mark, NetBackup will repeatedly attempt to clean it. It will clean up all staged images to the Low Water Mark.

Therefore, the fact that staged images are not cleaned up when the DSSU is below high water mark does not represent a problem by itself. As soon as it grows above High Water Mark, a cleanup of staged images is triggered.  

The High Water Mark setting is there as a flag to begin clearing staged images and prevent a full disk condition. The lower the High Water Mark setting is, the more vigorous NetBackup will be when cleaning staged images. The difference between the High and Low Water Mark setting determines how many staged images can be cleaned.

Note: NetBackup 6.5 Admin Guides contains a statement that High Water Mark is not applicable to Basic Disk storage units. This is incorrect - the High Water Mark does apply to Basic Disk as well as Advanced Disk storage units.





Legacy ID



316679


Article URL http://www.symantec.com/docs/TECH66149


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