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From "Mike Drob (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ACCUMULO-3303) funky performance with large WAL
Date Thu, 06 Nov 2014 17:28:33 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-3303?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14200502#comment-14200502
] 

Mike Drob commented on ACCUMULO-3303:
-------------------------------------

bq. So there is a known difference between large (>2G) WALs and the default size (1G).

Is this part of our docs anywhere? Logically, it makes sense, but it might not be obvious
to people that haven't thought about all of the implications of WAL sizing.

> funky performance with large WAL
> --------------------------------
>
>                 Key: ACCUMULO-3303
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-3303
>             Project: Accumulo
>          Issue Type: Bug
>          Components: logger, tserver
>    Affects Versions: 1.6.1
>            Reporter: Adam Fuchs
>         Attachments: 1GB_WAL.png, 2GB_WAL.png, 4GB_WAL.png, 512MB_WAL.png, 8GB_WAL.png,
WAL_disabled.png
>
>
> The tserver seems to get into a funky state when writing to a large write-ahead log.
I ran some continuous ingest tests varying tserver.walog.max.size in {512M, 1G, 2G, 4G, 8G}
and got some results that I have yet to understand. I was expecting to see the effects of
walog metadata management as described in ACCUMULO-2889, but I also found an additional behavior
of ingest slowing down for long periods when using a large walog size.
> The cluster configuration was as follows:
> {code}
> Accumulo version: 1.6.2-SNAPSHOT (current head of origin/1.6)
> Nodes: 4
> Masters: 1
> Slaves: 3
> Cores per node: 24
> Drives per node: 8x1TB data + 2 raided system
> Memory per node: 64GB
> tserver.memory.maps.max=2G
> table.file.compress.type=snappy (for ci table only)
> tserver.mutation.queue.max=16M
> tserver.wal.sync.method=hflush
> Native maps enabled
> {code}



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