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From "Eric Newton (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ACCUMULO-4112) MinC start/stop updates are always hsync'd
Date Wed, 20 Jan 2016 16:09:39 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-4112?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15108802#comment-15108802
] 

Eric Newton commented on ACCUMULO-4112:
---------------------------------------

I've updated the test. The test performs a series of Conditional updates on a table with many
tablets. I lowered the durability on the metadata table to flush.

I ran the test sending the "start MinC" and "stop MinC" writes to the WALog at different durabilities.
 The screenshot of the performance differences is shown.

It should be noted that the performance for a single tablet is always much faster, even with
full sync Durability.


> MinC start/stop updates are always hsync'd
> ------------------------------------------
>
>                 Key: ACCUMULO-4112
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-4112
>             Project: Accumulo
>          Issue Type: Bug
>          Components: tserver
>         Environment: Fluo testing on a 20-node cluster
>            Reporter: Eric Newton
>            Assignee: Eric Newton
>            Priority: Minor
>         Attachments: MinCFlushPerfTest.java, Sync-Flush-Log-Performance.png
>
>
> [~kturner] writes:
> {quote}
> I was running a Fluo test with 1.8.0-SNAP on my workstation.  My Fluo table had a ton
of tablets.   I was seeing terrible performance.   I started looking at the tserver and noticed
it was always calling hsync.  I tracked down the problem to the fact that when minc start
and stop events are written to the log they are always written w/ sync level.   My poor little
tserver was constantly minor compacting (probably had around 600 tablets that were all being
written to).  
> I changed the test config to create like 15 tablets and the performance was much better.
 All cores were 100% utilized, which was not the case when hsync was always called.
> {quote}



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