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From Kanwar Sangha <kan...@mavenir.com>
Subject RE: Replication Question
Date Mon, 04 Mar 2013 21:01:47 GMT
Keep in mind that even at consistency level ONE or LOCAL_QUORUM, the write is still sent to
all replicas for the written key, even replicas in other data centers. The consistency level
just determines how many replicas are required to respond that they received the write.

Is this true for Reads also ?



From: Kanwar Sangha [mailto:kanwar@mavenir.com]
Sent: 04 March 2013 14:54
To: user@cassandra.apache.org
Subject: Replication Question

Hi - If I configure a RF across 2 Data centres as below  and assuming 3 nodes per Data centre.

DC1: 2, DC2:2

I do a write with consistency level - local_quorum which ensures that there is no inter DC
latency. Now say 2 nodes in DC1 crash and I am doing a read with CL = One. Will it return
failure to client since the data is now only present in DC2 ? So  I would need to do a read
with CL = ALL/EACH_QUORUM to ensure that I always get the data even in case of crashes in
the local DC ?

Thanks,
Kanwar



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