Separation of Data (Cached/Non-Cached)
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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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