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Subject: Re: increased RF and repair, not working?
From: Tim Wintle <timwintle@gmail.com>
To: user@cassandra.apache.org
Date: Mon, 30 Jul 2012 13:14:20 +0100
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On Mon, 2012-07-30 at 14:40 +0300, Tamar Fraenkel wrote:
> Hi!
> To clarify it a bit more, 
> Let's assume the setup is changed to
> RF=3
> W_CL=QUORUM (or two for that matter)
> R_CL=ONE

> The setup will now work for both read and write in case of one node
> failure.
> What are the disadvantages, other than the disk space needed to
> replicate everything trice instead of twice? Will it affect also
> performance?

(I'm also running RF2, W_CL1, R_CL1 atm - so this is theoretical)

As I understand it, the most significant performance hit will be to the
variation in response time.

For example with R_CL1, (roughly) 1% of requests will be take more than
the worst 10% of server response times. With R_CL=QUORUM 2.8% of
requests will have the same latency. (assuming I've just calculated that
right)

Tim


> 
>