Solr Cloud reclaiming disk space from deleted documents

[Rishi Easwaran]

Hi All,

Running into an issue and wanted to see if anyone had some suggestions.
We are seeing this with both solr 4.6 and 4.10.3 code.
We are running an extremely update heavy application, with millions of writes 
and deletes happening to our indexes constantly.  An issue we are seeing is 
that solr cloud reclaiming the disk space that can be used for new inserts, by 
cleanup up deletes. 

We used to run optimize periodically with our old multicore set up, not sure if 
that works for solr cloud.

Num Docs:28762340
Max Doc:48079586
Deleted Docs:19317246

Version 1429299216227
Gen 16525463
Size 109.92 GB

In our solrconfig.xml we use the following configs.

    <indexConfig>
    <!-- Values here affect all index writers and act as a default unless 
overridden. -->
        <useCompoundFile>false</useCompoundFile>
        <maxBufferedDocs>1000</maxBufferedDocs>
        <maxMergeDocs>2147483647</maxMergeDocs>
        <maxFieldLength>10000</maxFieldLength>

        <mergeFactor>10</mergeFactor>
        <mergePolicy class="org.apache.lucene.index.TieredMergePolicy"/>
        <mergeScheduler 
class="org.apache.lucene.index.ConcurrentMergeScheduler">
            <int name="maxThreadCount">3</int>
            <int name="maxMergeCount">15</int>
        </mergeScheduler>
        <ramBufferSizeMB>64</ramBufferSizeMB>
        
    </indexConfig>


Any suggestions on which which tunable to adjust, mergeFactor, mergeScheduler 
thread counts etc would be great.

Thanks,
Rishi.