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From Nick Bailey <n...@datastax.com>
Subject Re: JMX Latency stats
Date Wed, 10 Jul 2013 17:36:37 GMT
The column family specific numbers are reporting latencies local to the
node. So a write/read that has reached the correct replica and just needs
to hit memory/disk.

The non column family specific numbers are reporting latencies from the
coordinator. So the latency from the time the coordinator receives a
write/read request, contacts the right replica(s), receives an internal
response and responds to the client.


On Wed, Jul 10, 2013 at 12:27 PM, Christopher Wirt <chris.wirt@struq.com>wrote:

> I was wondering if anyone knows the difference between the JMX latency
> stats and could enlighten me.****
>
> ** **
>
> We’ve been looking the column family specific stats and see really lovely
> < 3ms 99th percentile stats for all our families.****
>
>
> org.apache.cassandra.metrics:type=ColumnFamily,keyspace=mykeyspace,scope=mycolumnfamily,name=ReadLatency
> ****
>
> ** **
>
> Now, when we look at the overall client request read latency stats we see
> a far more inconsistent jagged 99th percentile flying between 5ms – 80ms *
> ***
>
> org.apache.cassandra.metrics:type=ClientRequest,scope=Read,name=Latency***
> *
>
> ** **
>
> ** **
>
> Thanks****
>
> ** **
>
> Chris****
>
> ** **
>
> ** **
>
> ** **
>
> ** **
>

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