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https://issues.apache.org/jira/browse/CASSANDRA-6746?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13944690#comment-13944690
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Pavel Yaskevich edited comment on CASSANDRA-6746 at 3/24/14 1:49 AM:
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[~enigmacurry] Thanks for the results, this looks promising although, one
question still remains - why is the dip for buffered-io patch happening. It
might be related to the last compaction combining 4 sstables into one... Can
you please do the following experiment - write the data, force a flush + major
compaction, once all compactions complete run the buffered-io-tweaks patch to
see if that deep in the middle of the run is actually caused by compaction
replacing pre-heated file set with completely cold file?
was (Author: xedin):
[~enigmacurry] Thanks for the results, this looks promising although I one
question for me remains why is there that deep for buffered-io patch, It might
be related to the last compaction combining 4 sstables into one... Can you
please do the following experiment - write the data, force a flush + major
compaction, once all compactions complete run the buffered-io-tweaks patch to
see if that deep in the middle of the run is actually caused by compaction
replacing pre-heated file set with completely cold file?
> 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-buffered-io-tweaks.png,
> 6746-patched.png, 6746.blockdev_setra.full.png,
> 6746.blockdev_setra.zoomed.png, 6746.buffered_io_tweaks.logs.tar.gz,
> 6746.txt, buffered-io-tweaks.patch,
> 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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