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From Huming Wu <huming...@gmail.com>
Subject Re: Cassandra performance
Date Tue, 18 Aug 2009 17:51:33 GMT
Here is the log4j setting (yes, it is just INFO):
log4j.rootLogger=INFO,stdout,R

I am not sure why the latency dropped during last 24 hours. One stats
I can see (from other reports) is that disk reads dropped 80% (reads
per sec) in last 24 hour which may explain the drop (less disk read).

I wanted to bring up this discussion on performance and ultimately
this is what matters the most to a production system (at least for
us). And I'd be glad to contribute (still fairly new to Cassandra
though) in this area. I hoped someone had done some tests and
therefore numbers can be cross examined. Performance numbers are
always dependent on the test data. I provided the data profile in my
original email already.

By the way to measure the performance, I inserted timing code to
get_slice and batch_insert, for example, for get_slice:

public List<ColumnOrSuperColumn> get_slice(...)
{
long t0 = System.currentTimeMillis();
....

long lat = System.currentTimeMillis() - t0)/(float)1000.0
return col;
}
And report this latency for every call to our in-house metrics system.
So this is server side report (not client).

To me, for the sustained read, cassandra uses too much cpu. Anyone has
seen the same thing?

Thanks,
Huming

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