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From Yang <teddyyyy...@gmail.com>
Subject Re: weird problem with performance
Date Fri, 21 Oct 2011 15:40:49 GMT
actually this is only an issue in HH, since HH writes all the stored
messages into the same row, so locking is a problem

2011/10/21 Jérémy SEVELLEC <jsevellec@gmail.com>:
> @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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