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MSDP question re full at 96% vs. high water mark at 98%

Level 3


When does full disk processing take place?  At 96% or 98% ?

And doesn't this all imply that a high water mark is probably best set to something like 90% (max)or probably (85%) so that clenup can occur before it gets full.  If so, then why is teh default 98%




Page 68 of the NetBackup v7.5 Deduplication Guide:
...says this:
About deduplication storage capacity 
The maximum deduplication storage capacity is 64 TBs. NetBackup reserves 4 percent of the storage space for the deduplication database and transaction logs. 
Therefore, a storage full condition is triggered at a 96 percent threshold. 
For performance optimization, Symantec recommends that you use a separate disk, volume, partition, or spindle for the deduplication database. If you use 
separate storage for the deduplication database, NetBackup still uses the 96 percent threshold to protect the data storage from any possible overload. 
If your storage requirements exceed the capacity of a media server deduplication node, do one of the following: 
- Use more than one media server deduplication node. 
- Use a PureDisk storage pool as the storage destination. 
  A PureDisk storage pool provides larger storage capacity; PureDisk also provides global deduplication. 
  See “About the deduplication storage destination” on page 22.
Only one deduplication storage path can exist on a media server. You cannot add another storage path to increase capacity beyond 64 TBs.
...but says this on page 82:
High water mark The High water mark setting is a threshold that invokes the following actions: 
- The High water mark indicates that the PureDiskVolume is full. When the PureDiskVolume reaches the High water mark, 
  NetBackup fails any backup jobs that are assigned to the storage unit. NetBackup also does not assign new jobs to a 
  storage unit in which the disk pool is full. 
  NetBackup also fails backup jobs if the PureDiskVolume does not contain enough storage for its estimated space requirement. 
- NetBackup begins image cleanup when the PureDiskVolume reaches the High water mark; image cleanup expires the 
  images that are no longer valid. NetBackup again assigns jobs to the storage unit when image cleanup reduces the 
  PureDiskVolume capacity to less than the High water mark. 
The default is 98%. 

Level 5
Employee Accredited Certified

This is a better break down on how it works:


It is based on your lowspace settings in your contentrouter.cfg.  After you hit the verylowspace threshold, no new data will be accepted on the diskpool.