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https://issues.apache.org/jira/browse/HBASE-10278?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13980752#comment-13980752
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Jonathan Hsieh commented on HBASE-10278:
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mhlog is with the multihlog patch in (on a trunk branch from last week) and on
by default. trunk was yesterday's trunk.
The two numbers are the average and stdev of 10 of the same consecutive runs.
99 is for the 99%tile, and 99.99 is for the 99.99%tile as reported by ITMTTR.
So to interpret the most interesting results with the patch has a higher
percentage that are adversely affected with high latencies. The 99%tile
latency for a puts when killing an RS using multihlog is 5.1ms, with a stddev
of 0.3ms. The 99.99%tile is 37647.2ms average with a 9888.0ms stddev. using
the old log it is 735.2 and 673.7 ms respetively. Next time i run this I'll
also get the worst cases, my guess is that they are the same or there is some
constant extra latency due to two wals in the multilog case.
> Provide better write predictability
> -----------------------------------
>
> Key: HBASE-10278
> URL: https://issues.apache.org/jira/browse/HBASE-10278
> Project: HBase
> Issue Type: New Feature
> Reporter: Himanshu Vashishtha
> Assignee: Himanshu Vashishtha
> Attachments: 10278-trunk-v2.1.patch, 10278-trunk-v2.1.patch,
> 10278-wip-1.1.patch, Multiwaldesigndoc.pdf, SwitchWriterFlow.pptx
>
>
> Currently, HBase has one WAL per region server.
> Whenever there is any latency in the write pipeline (due to whatever reasons
> such as n/w blip, a node in the pipeline having a bad disk, etc), the overall
> write latency suffers.
> Jonathan Hsieh and I analyzed various approaches to tackle this issue. We
> also looked at HBASE-5699, which talks about adding concurrent multi WALs.
> Along with performance numbers, we also focussed on design simplicity,
> minimum impact on MTTR & Replication, and compatibility with 0.96 and 0.98.
> Considering all these parameters, we propose a new HLog implementation with
> WAL Switching functionality.
> Please find attached the design doc for the same. It introduces the WAL
> Switching feature, and experiments/results of a prototype implementation,
> showing the benefits of this feature.
> The second goal of this work is to serve as a building block for concurrent
> multiple WALs feature.
> Please review the doc.
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