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https://issues.apache.org/jira/browse/ACCUMULO-2613?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13957915#comment-13957915
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Eric Newton commented on ACCUMULO-2613:
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I don't want to seem argumentative, because I really don't know if using this
cache for the WAL is a good idea, or not. But I can think of some issues:
* hopefully, in your clusters, recovery is an unusual operation
* WAL has to write to disk to survive power loss, making it a bad candidate
for RAM-only storage
* Others have purposefully turned off caching of WAL data to make memory
available for other things, since reading them at all is unusual
We already know we can improve recovery time by reducing the largest WAL size,
parallelizing read/sort, and computing a more optimal leaseRecovery timeout. I
would strongly suggest a more in-depth look into recovery before even
experimenting with HDFS caching.
> Take advantage of HDFS caching to improve MTTR
> ----------------------------------------------
>
> Key: ACCUMULO-2613
> URL: https://issues.apache.org/jira/browse/ACCUMULO-2613
> Project: Accumulo
> Issue Type: Improvement
> Reporter: Sean Busbey
> Priority: Critical
> Labels: recovery
> Fix For: 1.7.0
>
>
> Hadoop 2.3.0 added [HDFS
> caching|http://hadoop.apache.org/docs/current/hadoop-project-dist/hadoop-hdfs/CentralizedCacheManagement.html].
> We should use this for small internal use tables (like !METADATA) and we
> should probably have a configurable option to use it for tables, with a stern
> warning that it should only be enabled on small tables that will be
> frequently used.
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