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From "Alex Baranov (JIRA)" <>
Subject [jira] Commented: (SOLR-1379) Add RAMDirectoryFactory
Date Wed, 26 Aug 2009 03:17:59 GMT


Alex Baranov commented on SOLR-1379:

The second patch gives ability to have an index which exists purely in RAM. So, this is one
example. Actually this is a primary usage scenario.

The scenario with loading index into the RAM from the disk can be determined by the the combination
of all of the next requirements:
* Index is updated not through the Solr
* Index is very large (more than 100mil documents, containing more than 50 fields)
* Index updates affect about half of the documents each month.
* Search should be performed extremely fast
Since updates touch a lot of documents this can affect the user while OS caches are renewed
(according to our tests this can result in a lag of 5+ minutes while commit is happening).
Also we need to optimize the index after such huge updates which is also causes all caches
to be recreated, etc. To avoid the lag we can load the index into a RAM and reload it on a
scheduled basis using core reload feature (new index is used only after it is warmed up, etc.).

In addition to that, the test results for RAMDirectory and FSDirectory are different if the
user load is significant (e.g. 30+ concurrent requests): RAMDirectory is faster. Even when
we used mounted RAM disk as a storage for index and used FSDirectory this performed 2.5-3
times worse than RAMDirectory.

> Add RAMDirectoryFactory
> -----------------------
>                 Key: SOLR-1379
>                 URL:
>             Project: Solr
>          Issue Type: New Feature
>    Affects Versions: 1.3
>            Reporter: Alex Baranov
>            Priority: Minor
>             Fix For: 1.4
>         Attachments: SOLR-1379.patch, SOLR-1379.patch
> Implement class RAMDirectoryFactory to make possible using RAMDirectory by adding the
next configuration in solrconfig.xml:
> {code}<directoryFactory class="org.apache.solr.core.RAMDirectoryFactory"/>{code}

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