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From Rob Coli <rc...@palominodb.com>
Subject Re: Single Node Cassandra Installation
Date Tue, 06 Nov 2012 03:50:17 GMT
On Mon, Nov 5, 2012 at 12:23 PM, Drew Kutcharian <drew@venarc.com> wrote:
>> Switching from SimpleStrategy to RackAware can be a pain.
>
> Can you elaborate a bit? What would be the pain point?

If you don't maintain the same replica placement vis a vis nodes on
your cluster, you have to dump and reload.

Simple example, 6 node cluster RF=3 :

SimpleSnitch : A B C D E F

Data for natural range of A is also on B and C, the "next" nodes in the ring.

RackAwareSnitches : A B C D E F
"racks" they are in  :  1 1  2  2 3 3

Data for natural range of A is also on C and E, because despite not
being the next nodes in the RING, they are the first nodes in the next
rack.

If however you go from simple to rack aware and put your nodes in racks like :

A B C D E F
1 2 3 1 2 3

Then you have the same replica placement that SimpleStrategy gives you
and can safely switch strategies/snitches on an existing cluster. Data
for A is on B and C, on the same hosts, but for different reasons. Use
nodetool getendpoints to test.

=Rob

-- 
=Robert Coli
AIM&GTALK - rcoli@palominodb.com
YAHOO - rcoli.palominob
SKYPE - rcoli_palominodb

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