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https://issues.apache.org/jira/browse/HBASE-3976?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13051440#comment-13051440
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Karthick Sankarachary commented on HBASE-3976:
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If "hbase.rs.cacheblocksonwrite" is used sparingly, then I guess this a
non-issue. It'd be nice though to have different knobs to turn block caching on
for the "flush" case as opposed to the "compaction" case, considering that the
blocks in the snapshop being flushed are probably hotter than those in the
files being compacted.
> Disable Block Cache On Compactions
> ----------------------------------
>
> Key: HBASE-3976
> URL: https://issues.apache.org/jira/browse/HBASE-3976
> Project: HBase
> Issue Type: Improvement
> Components: regionserver
> Affects Versions: 0.90.3
> Reporter: Karthick Sankarachary
> Assignee: Nicolas Spiegelberg
> Priority: Minor
> Attachments: HBASE-3976-V3.patch, HBASE-3976-unconditional.patch,
> HBASE-3976.patch
>
>
> Is there a good reason to believe that caching blocks during compactions is
> beneficial? Currently, if block cache is enabled on a certain family, then
> every time it's compacted, we load all of its blocks into the (LRU) cache, at
> the expense of the legitimately hot ones.
> As a matter of fact, this concern was raised earlier in HBASE-1597, which
> rightly points out that, "we should not bog down the LRU with unneccessary
> blocks" during compaction. Even though that issue has been marked as "fixed",
> it looks like it ought to be reopened.
> Should we err on the side of caution and not cache blocks during compactions
> period (as illustrated in the attached patch)? Or, can we be selectively
> aggressive about what blocks do get cached during compaction (e.g., only
> cache those blocks from the recent files)?
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