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Date: Tue, 26 Jun 2012 08:16:41 -0700
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Subject: Re: Multi datacenter, WAN hiccups and replication
From: Karthik N <karthik.nar@gmail.com>
To: "user@cassandra.apache.org" <user@cassandra.apache.org>
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Since Cassandra optimizes and sends only one copy over the WAN, can I opt
in only for HH for WAN replication and avoid HH for the local quorum?
(since I know I have more copies)

On Tuesday, June 26, 2012, Mohit Anchlia wrote:

>
> On Tue, Jun 26, 2012 at 7:52 AM, Karthik N <karthik.nar@gmail.com<javascript:_e({}, 'cvml', 'karthik.nar@gmail.com');>
> > wrote:
>
>> My Cassandra ring spans two DCs. I use local quorum with replication
>> factor=3. I do a write in DC1 with local quorum. Data gets written to
>> multiple nodes in DC1. For the same write to propagate to DC2 only one
>> copy is sent from the coordinator node in DC1 to a coordinator node in
>> DC2 for optimizing traffic over the WAN (from what I have read in the
>> Cassandra documentation)
>>
>> Will a Wan hiccup result in a Hinted Handoff (HH) being created in
>> DC1's coordinator for DC2 to be delivered when the Wan link is up
>> again?
>>
>
> I have seen hinted handoff messages in the log files when the remote DC is
> unreachable. But this mechanism is only used for a the time defined in
> cassandra.yaml file.


-- 
Thanks, Karthik

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Since Cassandra optimizes and sends only one copy over the WAN, can I opt i=
n only for HH for WAN replication and avoid HH for the local quorum? (since=
 I know I have more copies)=A0<span></span><br><div><br>On Tuesday, June 26=
, 2012, Mohit Anchlia  wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex"><br>
<div class=3D"gmail_quote">On Tue, Jun 26, 2012 at 7:52 AM, Karthik N <span=
 dir=3D"ltr">&lt;<a href=3D"javascript:_e({}, &#39;cvml&#39;, &#39;karthik.=
nar@gmail.com&#39;);" target=3D"_blank">karthik.nar@gmail.com</a>&gt;</span=
> wrote:<br>

<blockquote style=3D"BORDER-LEFT:#ccc 1px solid;MARGIN:0px 0px 0px 0.8ex;PA=
DDING-LEFT:1ex" class=3D"gmail_quote">My Cassandra ring spans two DCs. I us=
e local quorum with replication<br>factor=3D3. I do a write in DC1 with loc=
al quorum. Data gets written to<br>

multiple nodes in DC1. For the same write to propagate to DC2 only one<br>c=
opy is sent from the coordinator node in DC1 to a coordinator node in<br>DC=
2 for optimizing traffic over the WAN (from what I have read in the<br>

Cassandra documentation)<br><br>Will a Wan hiccup result in a Hinted Handof=
f (HH) being created in<br>DC1&#39;s coordinator for DC2 to be delivered wh=
en the Wan link is up<br>again?<br></blockquote></div><br>I have seen hinte=
d handoff messages in the log files when the remote DC is unreachable. But =
this mechanism is only used for a the time defined in cassandra.yaml file.
</blockquote></div><br><br>-- <br>Thanks, Karthik<br>

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