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From Mohit Anchlia <mohitanch...@gmail.com>
Subject Re: Multi datacenter, WAN hiccups and replication
Date Tue, 26 Jun 2012 16:22:42 GMT
On Tue, Jun 26, 2012 at 8:16 AM, Karthik N <karthik.nar@gmail.com> wrote:

> 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)
>
>
>
I am not sure if I understand your question. In general I don't think you
can selectively decide on HH. Besides HH should only be used when the
outage is in mts, for longer outages using HH would only create memory
pressure.

>  On Tuesday, June 26, 2012, Mohit Anchlia wrote:
>
>>
>> On Tue, Jun 26, 2012 at 7:52 AM, Karthik N <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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