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From Karthik N <karthik....@gmail.com>
Subject Re: Multi datacenter, WAN hiccups and replication
Date Tue, 26 Jun 2012 15:16:41 GMT
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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