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https://issues.apache.org/jira/browse/CASSANDRA-12619?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15470990#comment-15470990
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Jon Haddad commented on CASSANDRA-12619:
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Possibly a dupe of https://issues.apache.org/jira/browse/CASSANDRA-8868 ?
> Improve JBOD throughput
> -----------------------
>
> Key: CASSANDRA-12619
> URL: https://issues.apache.org/jira/browse/CASSANDRA-12619
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Natale Galioto
> Labels: performance
> Fix For: 3.x
>
>
> Nodes with spinning disks have very limited throughputs during compactions.
> This is mainly due to
> [https://issues.apache.org/jira/browse/CASSANDRA-6696][CASSANDRA-6696] where
> each SSTable got "sticked" to one data directory only. In order to increase
> the performance during compactions, reads and writes should always happen on
> different directories, and a single data directory (for both reads or writes)
> should be used by no more than one compactor at time. The current throughput
> of a single spinning disk can get as low as 20MB/s due to r/w seeks
> penalties, but a compaction between two different spindles could easily get
> 100MB/s or more throughput. Since 6696 requires sstables to always be on the
> same data directory, even a compaction between two different data directory
> and then a "brutal" copy back to the "appropriate" directory could get an
> overall throughput of 50MB/s. Another option would be to let SStables "float"
> between two data directories only, and "switch" between them at every
> compaction.
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