How fragment size affects restore of a non-multiplexed image
bptm positions to the media fragment and the actual tape block that contains the first file to be restored. If fast-locate is available, bptm uses that for the positioning. If fast-locate is not available, bptm uses MTFSF/MTFSR (forward space filemark/forward space record) to do the positioning.
The first file is then restored.
After that, for every subsequent file to be restored, bptm determines where that file is, relative to the current position. It may be faster for bptm to position to that spot rather than to read all the data in between (if fast locate is available). In that case, bptm uses positioning to reach the next file instead of reading all the data in between.
If fast-locate is not available, bptm can read the data as quickly as it can position with MTFSR (forward space record).
Therefore, fragment sizes for non-multiplexed restores matter if fast-locate is NOT available. With smaller fragments, a restore reads less extraneous data. You can set the maximum fragment size for the storage unit on the Storage Unit dialog in the NetBackup Administration Console ().