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From Edward Capriolo <edlinuxg...@gmail.com>
Subject Re: Confusion regarding the terms "replica" and "replication factor"
Date Thu, 31 May 2012 03:07:02 GMT
http://answers.oreilly.com/topic/2408-replica-placement-strategies-when-using-cassandra/

As mentioned it does this:

The Network Topology Strategy places some replicas in another data
center and the remainder in other racks in the first data center, as
specified

Which is not what most would expect.
Assume your largish cluster is say 40 nodes in a data center.  3
copies get you quorum and a 48 port switch is pretty common. switches
can even be stacked sometimes 3 or 4 units so now you are talking 48x4
switch ports really make up one "rack".


On Wed, May 30, 2012 at 4:37 PM, Jeff Williams
<jeffw@wherethebitsroam.com> wrote:
>
> On May 30, 2012, at 10:32 PM, Edward Capriolo wrote:
>
>>
>> The snitch does use the datacenter and the rack but almost all
>> deployments use a single rack per DC, because when you have more then
>> one rack in a data center the NTS snitch has some logic to spread the
>> data between racks. (most people do not want this behavior)
>>
>
> Out of curiosity, why would most people not want this behaviour? It seems like a good
idea from a availability perspective.
>
> Jeff

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