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A Staged capacity managed storage destination means that NetBackup automatically manages the space on the (disk) destination. (This option is not available to tape storage units since tape capacity is considered to be infinite.)
The High water mark and Low water mark settings on the disk storage unit or disk pool determine how the space is managed.
See Low water mark setting .
If space is needed for new images, expired backup copies are removed from the storage destination when the storage unit reaches the high water mark. NetBackup removes backup images on the storage destination until the low water mark is reached.
If more space is needed, any images that are not past the Desired cache period can be deleted. However, an image is never deleted if it has not been duplicated to all destinations in the lifecycle, even if the image is past its retention period.
To see exactly when the storage destination reaches the low water mark value is difficult. A backup can occur at the same time as the expiration process occurs. After the backup is complete, the low water mark may be slightly greater than its lowest possible value.
The retention period for a staged capacity managed storage destination is not assured as it is for a fixed retention period. The Desired cache period becomes a target that NetBackup tries to maintain. If the space is not required, the backup data could remain on the storage destination longer than the Desired cache period indicates.
Symantec does not recommend allowing capacity-managed images and fixed-retention images to be written to the same volume in a disk storage unit. The volume may fill with fixed-retention images and not allow the space management logic to operate as expected.
Keep the following points in mind when configuring lifecycle destinations or selecting the storage location for a policy:
All lifecycles that write to a volume in a disk storage unit should write images of the same retention type: fixed or capacity-managed.
Do not write images both to a volume in a disk storage unit within a lifecycle and to the same volume (by the storage unit) directly from a policy.
Mark all disk storage units that are used with lifecycles as On demand only.
Check any storage unit groups to make sure that fixed and capacity-managed images cannot be written to the same volume in a disk storage unit.
Staged capacity managed is selectable for any disk storage unit that is allowed in a lifecycle. However, for the disk types that support single-instance store (SIS), Staged capacity managed functions to various degrees. In order for Staged capacity managed to operate, NetBackup must know how much space a backup image uses. With SIS enabled on the storage unit, NetBackup cannot know exactly how much space a particular backup image occupies.
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