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https://issues.apache.org/jira/browse/CASSANDRA-1825?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12968424#action_12968424
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Jonathan Ellis commented on CASSANDRA-1825:
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CASSANDRA-1379 is a similar issue but for row cache / BF check.

> Separation of Data (Cached/Non-Cached)
> --------------------------------------
>
>                 Key: CASSANDRA-1825
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1825
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Chris Goffinet
>             Fix For: 0.8
>
>
> At the moment Cassandra goes through the ROW-READ stage to fetch data from 
> the page cache, and if it's not in the page cache, it goes to disk.
> Data that is currently hot (in page cache) will block if all I/O threads are 
> busy reading from disk. We should seriously look at implementing a buffer 
> pool similar to MySQL for storing data in-memory, and our I/O threads be 
> dedicated to just going to disk.  I suggest studying how InnoDB does 
> scheduling as well, they have good lessons to learn from.
> Scaling I/O by thread's isn't going to be a good solution here either. I 
> would argue that going past 64 threads for I/O is just going to hurt overall 
> performance based on context switching.

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