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From aaron morton <aa...@thelastpickle.com>
Subject Re: Replication factor
Date Wed, 23 May 2012 10:00:25 GMT
RF is normally adjusted to modify availability (see http://thelastpickle.com/2011/06/13/Down-For-Me/)

> for example, if I have 4 nodes cluster in one data center, how can RF=2 vs RF=4 affect
read performance? If consistency level is ONE, looks reading does not need to go to another
hop to get data if RF=4, but it would do more work on read repair in the background.
Read Repair does not run at CL ONE.
When RF == number of nodes, and you read at CL ONE you will always be reading locally. But
with a low consistency.
If you read with QUORUM when RF == number of nodes you will still get some performance benefit
from the data being read locally.

Cheers


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

On 23/05/2012, at 9:34 AM, Daning Wang wrote:

> Hello,
> 
> What is the pros and cons to choose different number of replication factor in term of
performance? if space is not a concern.
> 
> for example, if I have 4 nodes cluster in one data center, how can RF=2 vs RF=4 affect
read performance? If consistency level is ONE, looks reading does not need to go to another
hop to get data if RF=4, but it would do more work on read repair in the background.
> 
> Can you share some insights about this?
> 
> Thanks in advance,
> 
> Daning 
> 


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