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From Chen Xinli <chen.d...@gmail.com>
Subject Re: cassandra for a inbox search with high reading qps
Date Wed, 18 Aug 2010 03:52:07 GMT
I'm using cassandra 0.6.4; there's a configuration option
DoConsistencyChecksBoolean in storage-conf.xml.
Is't that for read-repair ?

I will do a test for WRITE QUORUM, READ.ONE if it can meet our requirements.

2010/8/18 Edward Capriolo <edlinuxguru@gmail.com>

> On Tue, Aug 17, 2010 at 10:55 PM, Chen Xinli <chen.daqi@gmail.com> wrote:
> > Hi,
> >
> > We are going to use cassandra for searching purpose like inbox search.
> > The reading qps is very high, we'd like to use ConsitencyLevel.One for
> > reading and disable read-repair at the same time.
> >
> > For reading consistency in this condition, the writing should use
> > ConsistencyLevel.ALL. But the writing will fail if one node fails.
> > We want such a ConsistencyLevel for writing/reading that :
> > 1. writing will success if there is node alive for this key
> > 2. reading will not forward to a node that's just recovered and doing
> hinted
> > handoff
> >
> > So that, if some node fails, others nodes for replica will receive the
> data
> > and surve reading successfully;
> > when the failure node recovers,  it will receive hinted handoff from
> other
> > nodes and it'll not surve reading until hinted handoff is done.
> >
> > Does cassandra support the cases already? or should I modify the code to
> > meet our requirements?
> >
> > Thanks for any advices!
> >
> > --
> > Best Regards,
> > Chen Xinli
> >
>
> >>The reading qps is very high, we'd like to use ConsitencyLevel.One for
> reading and disable read-repair at the same time.
> You can not disable read repair, all reads no matter the
> ConsistencyLevel always repair. The CL only controls how many nodes to
> read from before returning data to the client.
>
> These two statements contradict.
> > For reading consistency in this condition, the writing should use
> ConsistencyLevel.ALL. But the writing will fail if one node fails.
> > 1. writing will success if there is node alive for this key
>
> Also regardless of the write ConsistencyLevel all writes are written
> to all nodes. If a target node is down HintedHandoff will queue the
> write up for when the node restarts * in (6.3 you can turn off Hinted
> Handoff)
>
> You may want to WRITE QUORUM, READ.ONE, with RF=3 you would need two
> failed nodes before seeing an UnavailableException. You still have
> pretty strong consistency (depending how you look at it) and fast
> reads.
>
> Check the IRC logs Ben "schooled" me over this a couple of days ago.
>



-- 
Best Regards,
Chen Xinli

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