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https://issues.apache.org/jira/browse/CASSANDRA-5863?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13734871#comment-13734871
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T Jake Luciani commented on CASSANDRA-5863:
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The Tricky part is tracking the "hotness" of these chunks. It needs to track
the number of times the chunk was decompressed in the last X seconds. If this
breaks some threshold then it would put it in the cache. This would keep
things like compaction from causing churn.
> Create a Decompressed Chunk Cache
> ---------------------------------
>
> Key: CASSANDRA-5863
> URL: https://issues.apache.org/jira/browse/CASSANDRA-5863
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: T Jake Luciani
>
> Currently, for every read, the CRAR reads each compressed chunk into a
> byte[], sends it to ICompressor, gets back another byte[] and verifies a
> checksum.
> This process is where the majority of time is spent in a read request.
> Before compression, we would have zero-copy of data and could respond
> directly from the page-cache.
> It would be useful to have some kind of Chunk cache that could speed up this
> process for hot data. Initially this could be a off heap cache but it would
> be great to put these decompressed chunks onto a SSD so the hot data lives on
> a fast disk similar to https://github.com/facebook/flashcache.
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