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https://issues.apache.org/jira/browse/CASSANDRA-792?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12833653#action_12833653
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Stu Hood commented on CASSANDRA-792:
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>From the patch:
----
The optional MergeFactor attribute is used to tune read vs write
performance for a ColumnFamily. The default value is 10. A lower
MergeFactor (minimum 2) will cause the ColumnFamily to be compacted
more frequently, leading to improved read performance at the cost of
decreased write performance. Accordingly, a higher MergeFactor (max 256)
will improve write performance, at the expense of read performance. For
example, a MergeFactor of 8 indicates that compaction should only happen
when more than 8 sstables of a similar size are present. MergeFactor
is directly tied to the number of file handles required by Cassandra: a
higher MergeFactor means more file handles.
----
Once #685 adds backpressure to storage proxy, this setting will have a much
more significant effect on write performance, since writes will be
backpressured by compactions.
> Configurable 'merge factor' for Column Families
> -----------------------------------------------
>
> Key: CASSANDRA-792
> URL: https://issues.apache.org/jira/browse/CASSANDRA-792
> Project: Cassandra
> Issue Type: New Feature
> Reporter: Stu Hood
> Fix For: 0.6
>
> Attachments:
> 0001-Use-logarithmic-bucket-sizes-and-always-compact-the-.patch,
> 0002-Cap-memory-usage-for-all-SSTables-being-compacted.patch,
> 0003-Hardcoded-per-cf-merge-factor.patch, 0004-Configurable-MergeFactor.patch
>
>
> Apache Lucene flushes and merges 'segments' in a manner that is quite similar
> to the treatment of Cassandra's sstables.
> One interesting and powerful tunable that Lucene provides is 'mergeFactor':
> EDIT: better link:
> http://hudson.zones.apache.org/hudson/job/Lucene-trunk/javadoc/core/org/apache/lucene/index/IndexWriter.html#setMergeFactor(int)
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