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From Batranut Bogdan <batra...@yahoo.com>
Subject Re: Load balancing issue with virtual nodes
Date Thu, 24 Apr 2014 21:20:15 GMT
I don't know about hector but the datastax java driver needs just one ip from the cluster and
it will discover the rest of the nodes. Then by default it will do a round robin when sending
requests. So if Hector does the same the patterb will againg appear.
Did you look at the size of the dirs?
That documentation is for C* 0.8. It's old. But depending on your boxes you might reach CPU
bottleneck. Might want to google for write path in cassandra..  According to that, there
is not much to do when writes come in...  
On Friday, April 25, 2014 12:00 AM, DuyHai Doan <doanduyhai@gmail.com> wrote:
 
I did some experiments.

 Let's say we have node1 and node2

First, I configured Hector with node1 & node2 as hosts and I saw that only node1 has high
CPU load

To eliminate the "client connection" issue, I re-test with only node2 provided as host for
Hector. Same pattern. CPU load is above 50% on node1 and below 10% on node2.

It means that node2 is playing as coordinator and forward many write/read request to node1

 Why did I look at CPU load and not iostat & al ?

 Because I have a very intensive write work load with read-only-once pattern. I've read here
(http://www.datastax.com/docs/0.8/cluster_architecture/cluster_planning) that heavy write
in C* is more CPU bound but maybe the info may be outdated and no longer true

 Regards

 Duy Hai DOAN




On Thu, Apr 24, 2014 at 10:00 PM, Michael Shuler <michael@pbandjelly.org> wrote:

On 04/24/2014 10:29 AM, DuyHai Doan wrote:
>
>  Client used = Hector 1.1-4
>>  Default Load Balancing connection policy
>>  Both nodes addresses are provided to Hector so according to its
>>connection policy, the client should switch alternatively between both nodes
>>
>
OK, so is only one connection being established to one node for one bulk write operation?
Or are multiple connections being made to both nodes and writes performed on both?
>
>-- 
>Michael
>
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