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Date: Mon, 27 Dec 2010 14:44:51 -0800
Message-ID: <AANLkTin2Ss8+gKHxTk6_Kx7-pqTZtE=AyasyKvjo8vSh@mail.gmail.com>
Subject: Re: read repair across datacenters?
From: Narendra Sharma <narendra.sharma@gmail.com>
To: user@cassandra.apache.org
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The comment in the cassandra.yaml says:
"specifies the probability with which read repairs should be invoked on *
non-quorum* reads"

Does this mean RR chance is applicable only for non-quorum reads?


Another question on same topic:
Will RR use one of the node in the other datacenter as coordinator instead
of sending the data to each replica (assuming they have old data)? This is
to reduce the amount of network traffic between datacenters.

-Naren

On Mon, Dec 27, 2010 at 1:26 PM, Brandon Williams <driftx@gmail.com> wrote:

> On Mon, Dec 27, 2010 at 3:17 PM, Shu Zhang <szhang@mediosystems.com>wrote:
>
>> Hi, I'm pretty new to cassandra and read a couple of contradictory things
>> on this topic. Does read repair get triggered across datacenters if you
>> query with a consistency level of local_quorum?
>>
>
> If the RR chance is 100% (default), it's triggered regardless of CL, which
> only controls how synchronously the repair is performed.
>
> -Brandon
>

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The comment in the cassandra.yaml says:<br>&quot;specifies the probability =
with which read repairs should be invoked on <b>non-quorum</b> reads&quot;<=
br><br>Does this mean RR chance is applicable only for non-quorum reads?<br=
>
<br><br><br>Another question on same topic:<br>Will RR use one of the node =
in the other datacenter as coordinator instead of sending the data to each =
replica (assuming they have old data)? This is to reduce the amount of netw=
ork traffic between datacenters.<br>
<br>-Naren<br><br><div class=3D"gmail_quote">On Mon, Dec 27, 2010 at 1:26 P=
M, Brandon Williams <span dir=3D"ltr">&lt;<a href=3D"mailto:driftx@gmail.co=
m">driftx@gmail.com</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quo=
te" style=3D"border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt=
 0.8ex; padding-left: 1ex;">
<div class=3D"gmail_quote"><div class=3D"im">On Mon, Dec 27, 2010 at 3:17 P=
M, Shu Zhang <span dir=3D"ltr">&lt;<a href=3D"mailto:szhang@mediosystems.co=
m" target=3D"_blank">szhang@mediosystems.com</a>&gt;</span> wrote:<br><bloc=
kquote class=3D"gmail_quote" style=3D"border-left: 1px solid rgb(204, 204, =
204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">


Hi, I&#39;m pretty new to cassandra and read a couple of contradictory thin=
gs on this topic. Does read repair get triggered across datacenters if you =
query with a consistency level of local_quorum?<br></blockquote><div><br>


</div></div><div>If the RR chance is 100% (default), it&#39;s triggered reg=
ardless of CL, which only controls how synchronously the repair is performe=
d.</div><div><br></div><font color=3D"#888888"><div>-Brandon</div></font></=
div>

</blockquote></div><br>

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