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https://issues.apache.org/jira/browse/ACCUMULO-1083?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13597249#comment-13597249
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Billie Rinaldi commented on ACCUMULO-1083:
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It looks like the permissions are configured so that administrators can edit
anyone's comment, and no one else is allowed to edit comments. This was copied
from Hadoop's setup. The system makes it really difficult to have custom
permissions -- administrators can't change the permissions, and when you ask
INFRA to do it typically they want to just copy some existing project's setup.
If people think it's important for everyone to be able to edit their own
comments, we can ask.
> add concurrency to HDFS write-ahead log
> ---------------------------------------
>
> Key: ACCUMULO-1083
> URL: https://issues.apache.org/jira/browse/ACCUMULO-1083
> Project: Accumulo
> Issue Type: Improvement
> Components: tserver
> Reporter: Adam Fuchs
> Fix For: 1.6.0
>
> Attachments: walog-performance.jpg
>
>
> When running tablet servers on beefy nodes (lots of disks), the write-ahead
> log can be a serious bottleneck. Today we ran a test of 1.5-SNAPSHOT on an
> 8-node (plus a master node) cluster in which the nodes had 32 cores and 15
> drives each. Running with write-ahead log off resulted in a >4x performance
> improvement sustained over a long period.
> I believe the culprit is that the WAL is only using one file at a time per
> tablet server, which means HDFS is only appending to one drive (plus
> replicas). If we increase the number of concurrent WAL files supported on a
> tablet server we could probably drastically improve the performance on
> systems with many disks. As it stands, I believe Accumulo is significantly
> more optimized for a larger number of smaller nodes (3-4 drives).
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