Space efficiency and sequentiality

Higher space efficiency means files are less fragmented and probably provide better sequential file access. A higher sequentiality indicates that the files are more contiguously allocated, and this will probably be better for sequential file access.

Space efficiency =

Total number of fragments used for file storage / (Largest fragment physical address - Smallest fragment physical address + 1)

Sequentiality =

(Total number of fragments - Number of grouped fragments +1) / Total number of fragments

If you find that your sequentiality or space efficiency values become low, you can use the reorgvg command to improve logical volume utilization and efficiency (see Reorganizing logical volumes). To improve file system utilization and efficiency, see File system reorganization.

In this example, the Largest fragment physical address - Smallest fragment physical address + 1 is: 0002539 - 0001584 + 1 = 956 fragments; total used fragments is: 8 + 48 + 812 = 868; the space efficiency is 868 / 956 (90.8 percent); the sequentiality is (868 - 3 + 1) / 868 = 99.8 percent.

Because the total number of fragments used for file storage does not include the indirect blocks location, but the physical address does, the space efficiency can never be 100 percent for files larger than 32 KB, even if the file is located on contiguous fragments.