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From Rob Coli <rc...@digg.com>
Subject Re: Can these stats be right?
Date Wed, 07 Apr 2010 19:26:43 GMT
On 4/7/10 12:16 PM, Mark Jones wrote:
>                  Read Latency: NaN ms.

./trunk/src/java/org/apache/cassandra/tools/NodeCmd.java
"
outs.println("\t\tRead Latency: " + String.format("%01.3f", 
cfstore.getRecentReadLatencyMicros() / 1000) + "
"

This call is telling you the (Read|Write|Range)Latency since the last 
time it was sampled. The other measure of latency is a value since the 
node started, exposed via the JMX interface as 
"org.apache.cassandra.service.StorageProxy.Attributes.TotalRangeLatencyMicros". 


If you are sure to not restart your node while doing your testing, this 
should provide you with the latency number you are looking for.

http://wiki.apache.org/cassandra/JmxInterface#org.apache.cassandra.service.StorageProxy.Attributes.TotalRangeLatencyMicros

The JmxInterface wiki page is currently missing a section on the per-CF 
attributes, but as cfstats shows, they are available via the JMX 
interface as well.

=Rob

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