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Optimizing eDirectory Performance

Novell Cool Solutions: Feature
By Linda Kennard

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Posted: 14 May 2003

In Novell eDirectory 8.5 and above, you can specify a block cache limit and an entry cache limit. Each cache boosts the performance of different eDirectory operations.

The block cache stores physical blocks from the database. This cache is most useful for boosting update operations. In the entry cache, the directory caches logical entries from the database, which reduces the time required to perform searches against eDirectory.

Distributing Memory

Generally speaking, the more blocks and entries that the directory can cache, the better it will perform overall. For databases that are less than 250 MB, the directory ideally should be able to cache the entire database in both the entry and block caches.

For large implementations of eDirectory, you must consider your usage requirements before you can optimize database cache settings. (More information on this subject will be available in LogicSource beginning next quarter.)

Generally, you should try to get as close to a 1:1 ratio of block cache to DIB Set as possible. For entry cache, you should try to get as close to a 1:2 or 1:4 ratio. For the best performance, exceed these ratios.

Using the Default Cache Settings

The default setting for each cache depends on whether the server where you're installing eDirectory holds a replica:

  • If the server does not hold a replica, the default setting is a hard memory limit of 16 MB, with 8 MB for block cache and 8 MB for entry cache.
  • If the server does hold a replica, the default setting is a dynamically adjusting limit of 51% of available memory, with a minimum threshold of 8 MB and a maximum threshold that keeps 24 MB available.

You can use either method for controlling cache memory consumption, but you cannot use them at the same time because they are mutually exclusive.

Novell recommends that for systems with 250 MB or less, you allot ample RAM and allow the system to dynamically adjust as it needs the RAM. Novell also recommends that you modify default database cache settings only when you are working with a large system (that is, a system with more than 250 MB).

Dynamically Adjusting

When using the dynamically adjusting limit, eDirectory periodically adjusts its memory consumption in response to the ebb and flow of memory consumption by other processes. The amount of memory eDirectory consumes is based on the limit you specify, which is a percentage of available physical memory. Using this percentage, eDirectory calculates a memory limit at fixed intervals (every 15 seconds, by default).

In addition to setting this percentage, you can set a maximum and minimum threshold, which represent the number of bytes to which eDirectory will adjust. You can set these thresholds as either the number of bytes to use or the number of bytes to leave available. If the minimum and maximum threshold limits are incompatible, eDirectory follows the minimum threshold limit.

For example, suppose that you specify the following settings:

  • Minimum threshold: 8 MB
  • Percentage of available physical memory to use: 75
  • Maximum threshold: Keep 10 MB available

Now suppose that when eDirectory attempts to adjust its cache limit it finds 16 MB of available physical memory, 75% of which is 12 MB. eDirectory determines whether 12 MB falls within the range of minimum and maximum thresholds. In this case, the maximum threshold requires that 10 MB must remain available, so eDirectory sets the limit to 6 MB. However, the minimum threshold is 8 MB, so eDirectory resets the final limit to 8 MB.

This tip is an abridged excerpt from a chapter titled "Proactive Maintenance: Novell eDirectory" in Global Tree Integration: Operations Guide, a Novell consulting report. In addition to the information above, this chapter provides in-depth explanations about (and tips on) eDirectory health checks, hardware upgrades/replacements, and recovery. You can access this and other consulting reports as well as other advanced resources, such as LogicSource, through Novell Technical Subscriptions. For more information, visit

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