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https://issues.apache.org/jira/browse/CASSANDRA-6357?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13945705#comment-13945705
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dan jatnieks edited comment on CASSANDRA-6357 at 3/24/14 9:19 PM:
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I can also go back and re-run 2.0 w/patch on the same machine used for 2.1 ...
but that patch isn't quite the same as the 2.1 code either...
I was wondering if changes to flushing and/or compaction in 2.1 already lessen
the contention that was present in 2.0?
was (Author: djatnieks):
I can also go back and re-run 2.0 w/patch on the same machine used for 2.1 ...
but that patch isn't quite the same as the 2.1 code either...
> Flush memtables to separate directory
> -------------------------------------
>
> Key: CASSANDRA-6357
> URL: https://issues.apache.org/jira/browse/CASSANDRA-6357
> Project: Cassandra
> Issue Type: New Feature
> Components: Core
> Reporter: Patrick McFadin
> Assignee: Jonathan Ellis
> Priority: Minor
> Labels: performance
> Fix For: 2.1 beta1
>
> Attachments: 6357-v2.txt, 6357.txt,
> c6357-2.1-stress-write-adj-ops-sec.png,
> c6357-2.1-stress-write-latency-99th.png,
> c6357-2.1-stress-write-latency-median.png,
> c6357-stress-write-latency-99th-1.png
>
>
> Flush writers are a critical element for keeping a node healthy. When several
> compactions run on systems with low performing data directories, IO becomes a
> premium. Once the disk subsystem is saturated, write IO is blocked which will
> cause flush writer threads to backup. Since memtables are large blocks of
> memory in the JVM, too much blocking can cause excessive GC over time
> degrading performance. In the worst case causing an OOM.
> Since compaction is running on the data directories. My proposal is to create
> a separate directory for flushing memtables. Potentially we can use the same
> methodology of keeping the commit log separate and minimize disk contention
> against the critical function of the flushwriter.
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