6.19. Fragmentation Example

> xfs_db –r device
xfs_db: freesp
   from      to extents  blocks    pct
      1       1   94807   94807   1.36
      2       3   63041  145012   2.08
      4       7   30374  152890   2.19
      8      15   19437  207742   2.98
     16      31   15173  331559   4.76
     32      63   14099  636086   9.13
     64     127   16804 1497220  21.48
    128     255    8390 1470464  21.10
    256     511    3003 1033383  14.83
    512    1023     810  551813   7.92
   1024    2047     258  370811   5.32
   2048    4095     101  282202   4.05
   4096    8191      27  145550   2.09
xfs_db: frag -d
actual 45966, ideal 12398, fragmentation factor 73.03%
xfs_db: frag -f
actual 2104856, ideal 2100484, fragmentation factor 0.21%

Note

The fragmentation factor value can be misleading.

It is derived from (actual - ideal) / (ideal) so an average of 5 extents per file will yield 80%. For multi-gigabyte files, 5 extents is not harmful, and the 80% is not representative of a problem.