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From "Jonathan Ellis (JIRA)" <>
Subject [jira] [Resolved] (CASSANDRA-1825) Separation of Data (Cached/Non-Cached)
Date Mon, 11 Apr 2011 15:34:05 GMT


Jonathan Ellis resolved CASSANDRA-1825.

       Resolution: Later
    Fix Version/s:     (was: 0.8)

> Separation of Data (Cached/Non-Cached)
> --------------------------------------
>                 Key: CASSANDRA-1825
>                 URL:
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Chris Goffinet
> 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

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