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https://issues.apache.org/jira/browse/SOLR-1379?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12752543#action_12752543
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Grant Ingersoll commented on SOLR-1379:
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{quote}
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.
{quote}
Can you share your performance tests? Also, not sure why a very large index is
a use case _for_ RAMDirectory implementation.
Finally, storing the Directories in a Map doesn't seem like a good idea.
I think we should mark this for 1.5, so it can be revisited then.
> Add RAMDirectoryFactory
> -----------------------
>
> Key: SOLR-1379
> URL: https://issues.apache.org/jira/browse/SOLR-1379
> Project: Solr
> Issue Type: New Feature
> Affects Versions: 1.3
> Reporter: Alex Baranov
> Priority: Minor
> Fix For: 1.5
>
> 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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