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From James Masson <james.mas...@opigram.com>
Subject Re: Cassandra read throughput with little/no caching.
Date Mon, 24 Dec 2012 12:28:22 GMT


On 21/12/12 17:56, Yiming Sun wrote:
> James, you could experiment with Row cache, with off-heap JNA cache, and
> see if it helps.  My own experience with row cache was not good, and the
> OS cache seemed to be most useful, but in my case, our data space was
> big, over 10TB.  Your sequential access pattern certainly doesn't play
> well with LRU, but giving the small data space you have, you may be able
> to fit the data from one column family entirely into the row cache.
>
>

I've done some experimenting today with JNA/row cache. Extra 500Mb of 
heap, 300Mb row cache, latest JNA, set caching=ALL in the schema for all 
column families in this keyspace.

Getting average 5% row cache hit rate - no increase in cassandra 
throughput, and increased disk read I/O, basically because I've 
sacrificed Linux disk cache for the cassandra row-cache.

Load average was 4 (2cpu boxes) for the duration of the cycle, where it 
was about 2 before, basically because of the disk I/O I think.

So, I think I'll disable row caching again...

James M

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