Defining NetBackup Estimated Tape Capacity > NetBackup Estimated Tape Capacity Overview
Version 9.1
NetBackup Estimated Tape Capacity Overview
For NetBackup, some enterprise environments freeze or suspend tape media and do not allow their backup tapes to fill to capacity. In this situation, a StorageConsole database table (apt_nbu_tape_capacity_est) can be updated to override the standard estimated capacity calculation. In this table, values for Volume Pool ID, Media Type, and Estimated Capacity will be used to override the estimated capacity calculation. See Estimated Capacity Notes.
When values are supplied in this table, the NetBackup estimated capacity calculations will first determine the average size of full tapes—by tape type and volume pool. If this value is less than the value provided in the apt_nbu_tape_capacity_est table, the value in the table will be used for the estimated capacity.
Various StorageConsole backup media reports use an estimated capacity calculation:
Tape Media Summary
Tape Media Detail
Media Availability Forecast
Media Consumption Forecast
Estimated Capacity Notes
Every time tape data is captured, StorageConsole recalculates the estimated tape capacity for the tape media type and volume pool combination. It takes into consideration the written KBs for the media type and volume pool for full tapes and then stores the average as the estimated tape capacity. Initially, when there is not enough data captured, this value may look low compared to the capacity stated by the vendor. Over time, the estimated capacity improves to the actual number of KBs that is being written to the tapes. Note that the amount of data that fits on the tapes differs based on the compression algorithm used and the type of data that is being backed up, which results in different compression ratios.