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From aaron morton <aa...@thelastpickle.com>
Subject Re: weird problem with performance
Date Thu, 20 Oct 2011 20:37:54 GMT
It's unlikely that HH is the issue. (Disclaimer, am not familiar with HH in 1.0, i know it's
changes a bit)

Take a look at the TP Stats, what's happening ?

Cheers

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

On 20/10/2011, at 10:10 AM, Jérémy SEVELLEC wrote:

> Ok.
> 
> I think a degration could be normal because your cluster is in a degraded state when
a node is down.
> 
> With a replication_factor of 3 and with a 3 nodes cluster, each data you write is replicated
on each node. As One node is down, when writing, it's impossible to send a replica on the
down node and hints are send : http://www.datastax.com/docs/1.0/dml/about_writes#hinted-handoff-writes
> And it could be more expensive to achieve QUORUM when you read in that context.
> 
> It may be one explanation. You can turn cassandra log into debug level to see what happen
when when there is a down node.
> 
> 2011/10/19 Yang <teddyyyy123@gmail.com>
> 3
> 
> sorry forgot this important info
> 
> On Oct 19, 2011 11:31 AM, "Jérémy SEVELLEC" <jsevellec@gmail.com> wrote:
> Hi, what is your replication_factor?
> 
> 2011/10/19 Yang <teddyyyy123@gmail.com>
> I'm using a cassandra version compiled from 1.0.0  github HEAD.
> 
> I have 3 nodes, A B and C,  on node A I run a client, which talks only
> to B as the coordinator.
> 
> the performance is pretty good, a QUORUM read+write  takes < 10ms.
> 
> but then I shutdown C, quickly the performance starts to degrade, and
> QUORUM read+write time steadily increase to about 300ms.
> 
> if I shutdown A and keep C, I observe the same effect.
> 
> 
> I understand that "2 out of 3" is going to give you faster response
> than "2 out of 2", but  the difference should not be that dramatic as
> 10ms vs 300ms.
> 
> any possible reasons for this?(or how to debug this?)
> 
> Thanks
> Yang
> 
> 
> 
> -- 
> Jérémy
> 
> 
> 
> -- 
> Jérémy


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