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From aaron morton <aa...@thelastpickle.com>
Subject Re: read request distribution
Date Wed, 14 Nov 2012 04:30:41 GMT
> As soon as one CF is created, the column changes to Effective Ownership 
There has to be a user defined keyspace to calculate effective ownership.

Effective Ownership is calculated for all keyspaces if the share the same RF, and for a named
KS if specified. It's the % of the total cluster data stored on that node for the named KS
or all keyspaces. 

Cheers
-----------------
Aaron Morton
Freelance Developer
@aaronmorton
http://www.thelastpickle.com

On 14/11/2012, at 9:43 AM, Wei Zhu <wz1975@yahoo.com> wrote:

> I am new to Cassandra, and 1.1.6 is the only version I have tested. Not sure about the
old behavior, for 1.1.6, my observation is that for brand new cluster (with no CF created),
it shows Ownership from nodetool ring, the value is 100/<nodes>. As soon as one CF is
created, the column changes to Effective Ownership and the formula seems to be 100*<replication
factor>/<nodes> as Kirk mentioned. .Theoretically, different keyspace can have different
replication factor. Not sure how Effective Ownership is calculated in that cases. Just curious
anyone knows?
> 
> Thanks.
> -Wei
> 
> From: Kirk True <kirk@mustardgrain.com>
> To: user@cassandra.apache.org 
> Sent: Monday, November 12, 2012 4:24 PM
> Subject: Re: read request distribution
> 
> Somewhat recently the Ownership column was changed to Effective Ownership. 
>  
> Previously the formula was essentially 100/<nodes>. Now it's 100*<replication
factor>/<nodes>. So in previous releases of Cassandra it would be 100/12 = 8.33,
now it would be closer to 25% (8.33*3 (assuming a replication factor of three)).
>  
> Kirk
>  
> On Mon, Nov 12, 2012, at 03:52 PM, Ananth Gundabattula wrote:
>> 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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