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From Ananth Gundabattula <agundabatt...@gmail.com>
Subject Re: read request distribution
Date Mon, 12 Nov 2012 23:52:39 GMT
Hi all,

On an unrelated observation of the below readings, it looks like all the 3
nodes own 100% of the data. This confuses me a bit. We have a 12 node
cluster with RF=3 but the effective ownership is shown as 8.33 % .

So here is my question. How is the ownership calculated : Is Replica factor
considered in the ownership calculation ? ( If yes , then 8.33 % ownership
of a cluster seems wrong to me . If not 100% ownership for a node cluster
seems wrong to me. Am I missing something in the calculation?

Regards,
Ananth

On Fri, Nov 9, 2012 at 4:37 PM, Wei Zhu <wz1975@yahoo.com> wrote:

> Hi All,
> I am doing a benchmark on a Cassandra. I have a three node cluster with
> RF=3. I generated 6M rows with sequence  number from 1 to 6m, so the rows
> should be evenly distributed among the three nodes disregarding the
> replicates.
> I am doing a benchmark with read only requests, I generate read request
> for randomly generated keys from 1 to 6M. Oddly, nodetool cfstats, reports
> that one node has only half the requests as the other one and the third
> node sits in the middle. So the ratio is like 2:3:4. The node with the most
> read requests actually has the smallest latency and the one with the least
> read requests reports the largest latency. The difference is pretty big,
> the fastest is almost double the slowest.
> All three nodes have the exactly the same hardware and the data size on
> each node are the same since the RF is three and all of them have the
> complete data. I am using Hector as client and the random read request are
> in millions. I can't think of a reasonable explanation.  Can someone please
> shed some lights?
>
> Thanks.
> -Wei
>

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