The Directory Proxy Server includes a tool, global-index-size, to help you estimate the size in memory of your global indexes. You can estimate the size of more than one index in a single invocation by providing multiple sets of options. The tool creates its estimate using the following information:
  • Number of keys in the index. For example, for the built-in RDN index, the number of keys is the total number of entries in the Directory Server that are immediately below the balancing point. Entries more than one level below the balancing point, as well as entries that are not subordinate to the balancing point, will not be contained in the RDN index. For attribute indexes, the number of keys will be the number of unique values for that attribute in the entry-balanced portion of the data.

  • Average size of each key, in bytes. For attributes indexes, the key is simply the attribute value. For the built-in RDN index, the key is the RDN directly below the balancing base DN. For example, for the DN uid=user.0,dc=example,dc=com under the balancing base DN of dc=example,dc=com, the key size is 10 bytes (the number of bytes in the RDN uid=user.0).

  • Estimated number of keys. This value corresponds to the maximum number of keys you expect in your Directory Server. The number of keys is provided in the index-size configuration property of the global-attribute-index object when you configure an attribute index. For the built-in RDN index, the configured number of keys is provided in the rdn-index-size property. If you do not provide a value, the tool assumes that the configured number of keys is the same as the actual number of keys.

  • Run the global-index-size to estimate the size of two separate indexes, both with 10,000,000 keys but with differing average key sizes. The configured number of keys is assumed to be equal to the actual number of keys:
    $ bin/global-index-size --numKeys 10000000 \ 
      --averageKeySize 11 --numKeys 10000000 \
      --averageKeySize 15    
    Num Keys : Cfg. Num Keys : Avg. Key Size : Est. Memory Size
    10000000 : 10000000      : 11            : 159 mb
    10000000 : 10000000      : 15            : 197 mb