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vx_dexh_sz - determine the large directory hashing threshold size


You must set this tunable to a constant value.
Minimum 16383
Maximum 4294967295
Default 196607
Special values
  Disables the large directory feature. Existing large directory hashes are removed whenever the hashes would normally be updated.


The vx_dexh_sz tunable determines the threshold for creating a large directory hash. When the number of directory entries exceeeds the vx_dexh_sz threshold value, a large directory hash is created. The vx_dexh_sz is a dynamic tunable.

    Who is expected to change this tunable?

Any privileged user can change this value. The default state should be appropriate for most environments.

    Restrictions on changing

None. The vx_dexh_sz tunable is dynamic; tuning takes effect immediately on the running system.

    What other tunable values should be changed at the same time?


    When should the value of this tunable be raised?

If file system contains directories with large numbers of files and a hash for quick lookups is not required, then you can raise the value for the vx_dexh_sz tunable.

    What are the side effects of raising the value?

None. Raising the value of the vx_dexh_sz tunable does not have any side effects. However, lookups will take a longer time due to the removing of the hash for directories that have a lower number of files than the vx_dexh_sz tunable value.

    When should the value of this tunable be lowered?

If performance of lookup operations on directories with a small number of files needs to be improved, then you can lower the value of the vx_dexh_sz tunable.

    What are the side effects of lowering the value?

Lowering the value of the vx_dexh_sz tunable results in a greater amount of space used by directories, as hashes are stored on disk.


VxFS kernel tunable parameters are release specific. This parameter may be removed or the default value and usage may change in future releases. See the Storage Foundation Release Notes for information about changes to parameters, if any.

VxFS 7.4 vx_dexh_sz(5)