The benefits of having compact entries in the database are available today with Sun Directory Server Enterprise Edition 7 and Sun OpenDS Standard Edition 2.2, writes Ludovic Poitou in his blog Sun Directory Compresses Data for Better Performance, adding that both solutions are helping customers to reduce the overall cost of ownership of the directory services.

The entry compression feature is also available in the technology that will power future versions of Sun Directory Enterprise Edition: the OpenDS project, Poitou notes. In OpenDS, there are 2 options to reduce the size of entries stored in the database. The first one is called entry compaction, and it's enabled by default. The entry compaction feature removes all references to attribute names and replaces them with small identifiers. The second option is actually entry compression, which will use the popular ZLib algorithm. This option is not activated by default, but the command he includes in his blog enables it.

Poitou presents tabular results of database size using OpenDS 2.2.0 with no compact encoding, with default compact encoding, and with compression enabled. The table compares the size of the entry record within the database as well as the overall size of the database which also includes indexes (default OpenDS settings).

A second table illustrates the import times for the three different modes for storing entries, for the three sample data files.

What Poitou concludes is that enabling compression does result in a smaller disk use with that sample data (fully random values), but does come with a performance penalty at least at import time, less than 10%, though the penalty increases with the number of entries.

Changing from the default mode (compacted) to uncompacted mode does not give any real advantage in performance, he writes, but does increase the disk space usage. So, he concludes, there is no apparent value in changing these settings in OpenDS.

Poitou refers to Brad Diggs' blog, Directory Data Priming Strategies, which points out that directory data priming can promote more consistent directory server performance for directory service architectures that are designed to contain all of the directory data in the ZFS ARC either via sufficiently large DRAM or flash technologies.

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