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https://issues.apache.org/jira/browse/HBASE-23066?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16937040#comment-16937040
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Sean Busbey commented on HBASE-23066:
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I'd like to see some benchmarking to show effectiveness please.
Also some measurement of impact when the working set doesn't fit in the cache.
> Allow cache on write during compactions when prefetching is enabled
> -------------------------------------------------------------------
>
> Key: HBASE-23066
> URL: https://issues.apache.org/jira/browse/HBASE-23066
> Project: HBase
> Issue Type: Improvement
> Components: Compaction, regionserver
> Affects Versions: 1.4.10
> Reporter: Jacob LeBlanc
> Assignee: Jacob LeBlanc
> Priority: Minor
> Fix For: 1.5.0, 2.3.0
>
> Attachments: prefetchCompactedBlocksOnWrite.patch
>
>
> In cases where users care a lot about read performance for tables that are
> small enough to fit into a cache (or the cache is large enough),
> prefetchOnOpen can be enabled to make the entire table available in cache
> after the initial region opening is completed. Any new data can also be
> guaranteed to be in cache with the cacheBlocksOnWrite setting.
> However, the missing piece is when all blocks are evicted after a compaction.
> We found very poor performance after compactions for tables under heavy read
> load and a slower backing filesystem (S3). After a compaction the prefetching
> threads need to compete with threads servicing read requests and get
> constantly blocked as a result.
> This is a proposal to introduce a new cache configuration option that would
> cache blocks on write during compaction for any column family that has
> prefetch enabled. This would virtually guarantee all blocks are kept in cache
> after the initial prefetch on open is completed allowing for guaranteed
> steady read performance despite a slow backing file system.
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