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https://issues.apache.org/jira/browse/CASSANDRA-6746?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13938239#comment-13938239
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Pavel Yaskevich commented on CASSANDRA-6746:
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I guess I should have been clearer about this one, we actually want readahead
to be set to bigger number or default, that would speed up sequential part of
the read significantly, because kernels' adaptive readahead logic would kick in
and detect that file is being read sequential and do a right thing.
The test I asked you to do should have uncovered effect of readahead on our
reads which is pretty significant but quiet the opposite on HDD vs. SDD, still
this gives us pretty good picture.
> Reads have a slow ramp up in speed
> ----------------------------------
>
> Key: CASSANDRA-6746
> URL: https://issues.apache.org/jira/browse/CASSANDRA-6746
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Reporter: Ryan McGuire
> Assignee: Benedict
> Labels: performance
> Fix For: 2.1 beta2
>
> Attachments: 2.1_vs_2.0_read.png, 6746-patched.png,
> 6746.blockdev_setra.full.png, 6746.blockdev_setra.zoomed.png, 6746.txt,
> cassandra-2.0-bdplab-trial-fincore.tar.bz2,
> cassandra-2.1-bdplab-trial-fincore.tar.bz2
>
>
> On a physical four node cluister I am doing a big write and then a big read.
> The read takes a long time to ramp up to respectable speeds.
> !2.1_vs_2.0_read.png!
> [See data
> here|http://ryanmcguire.info/ds/graph/graph.html?stats=stats.2.1_vs_2.0_vs_1.2.retry1.json&metric=interval_op_rate&operation=stress-read&smoothing=1]
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