NetBackup disk volume capacity and usage reference
NetBackup determines the space available for backups on a volume by using the following formula:
Available space equals free_space plus potential_free_space minus committed_space.
The potential_free_space value is used only for a disk volume that is capacity managed. A disk volume is capacity managed when its disk pool is capacity managed. A disk pool is capacity managed when it is a destination in a storage lifecycle policy and the is .
Table: Disk capacity values describes the capacity values that NetBackup uses for space calculations.
Table: Disk capacity values
Field | Description |
|---|---|
total_capacity | The total size of the disk. This value is derived from the file system and is updated at 1-minute intervals. |
total_phys_capacity | For the purposes of AdvancedDisk, total_capacity and total_phys_capacity should have the same values. |
free_space | The amount of free space on the disk. This value is derived from the file system and is updated at 1-minute intervals. |
free_phys_space | For the purposes of AdvancedDisk, free_space and free_phys_space should have the same values. |
potential_free_space | The sum of all of the fragments on the disk that NetBackup duplicated as part of a storage lifecycle policy and that are eligible for expiration. A fragment becomes eligible for expiration when it has been duplicated successfully. NetBackup calculates potential_free_space a the end of duplication sessions and expiration sessions. The potential_free_space value may become stale between computations. However, the next computation provides an accurate value. |
committed_space | The estimated size of all of the jobs-in-progress that write to the volume, based on the following:
|
precommitted_space | The precommitted_space is a helper value for committed_space. NetBackup decrements the value while a backup job runs. Each time NetBackup updates the capacity and free space information, NetBackup updates the value of committed_space to the current value of precommitted_space. This process ensures that all capacity-related values are updated at the same time to provide the most accurate usage description for the disk volume. |