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From Jérémy SEVELLEC <jsevel...@gmail.com>
Subject Re: weird problem with performance
Date Fri, 21 Oct 2011 07:47:44 GMT
@Araron you're right and i was wrong!

2011/10/20 Yang <teddyyyy123@gmail.com>

> found it , https://issues.apache.org/jira/browse/CASSANDRA-3387
>
> On Thu, Oct 20, 2011 at 1:37 PM, aaron morton <aaron@thelastpickle.com>
> wrote:
> > 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
> >
> >
>



-- 
Jérémy

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