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From Jonathan Ellis <jbel...@gmail.com>
Subject Re: RackAwareStrategy Documentation Disparity
Date Fri, 11 Jun 2010 19:16:01 GMT
Then the wiki is incorrect.

On Fri, Jun 11, 2010 at 11:33 AM, Aaron Blew <aaronblew@gmail.com> wrote:
> That makes sense.  It still seems to conflict with what's stated in the
> wiki:
> "...the remaining N-2 replicas, if any, are placed on the first nodes along
> the ring in the *same* rack as the first"
> -Aaron
>
> On Fri, Jun 11, 2010 at 11:20 AM, Jonathan Ellis <jbellis@gmail.com> wrote:
>>
>> You're mis-parsing the first.  It says "place one replica in a
>> different datacenter, and the others on different racks in the same
>> one," where the antecedent of "one" is "datacenter," not rack.
>>
>> On Fri, Jun 11, 2010 at 11:09 AM, Blew, Aaron <aaron.blew@iovation.com>
>> wrote:
>> > The first text says the N-2 replicas are placed in the same rack while
>> > the
>> > second text indicates that the N-2 replicas will be placed in different
>> > racks.
>> > Am I missing something?
>> > -Aaron
>> > ---
>> > Aaron Blew -
>> > Sr. Infrastructure Engineer | The Automator
>> > iovation - The Power of Reputation™
>> > aaron.blew@iovation.com
>> > On Jun 11, 2010, at 10:48 AM, Jonathan Ellis wrote:
>> >
>> > I'm not sure what parts of these you think are in conflict.
>> >
>> > On Fri, Jun 11, 2010 at 10:34 AM, Blew, Aaron <aaron.blew@iovation.com>
>> > wrote:
>> >
>> > Hello,
>> >
>> > I was browsing the docs for the RackAware replication strategy and saw
>> > this
>> > on the wiki:
>> >
>> > "RackAwareStrategy: replica 2 is placed in the first node along the ring
>> > the
>> > belongs in another data center than the first; the remaining N-2
>> > replicas,
>> > if any, are placed on the first nodes along the ring in the *same* rack
>> > as
>> > the first"
>> >
>> > However the storage.conf comments say the following:
>> >
>> > "Strategy: Setting this to the class that implements
>> > IReplicaPlacementStrategy will change the way the node picker works.
>> >  Out of
>> > the box, Cassandra provides
>> > org.apache.cassandra.locator.RackUnawareStrategy
>> > and org.apache.cassandra.locator.RackAwareStrategy (place one replica in
>> > a
>> > different datacenter, and the others on different racks in the same
>> > one.)"
>> >
>> > To me the comments in storage.conf make more sense since you'd want
>> > datacenter diversity for the data as well as rack level diversity within
>> > the
>> > local datacenter.  Which one is accurate?  Is the disparity a result of
>> > the
>> > wiki page not being updated after the behavior changed with a release?
>> >
>> > Thanks all,
>> >
>> > -Aaron
>> >
>> > ---
>> >
>> > Aaron Blew -
>> >
>> > Sr. Infrastructure Engineer | The Automator
>> >
>> > iovation - The Power of Reputation™
>> >
>> > aaron.blew@iovation.com
>> >
>> >
>> >
>> > iovation
>> >
>> > 111 SW Fifth Avenue
>> >
>> > Suite 3200
>> >
>> > Portland, OR 97204
>> >
>> > http://www.iovation.com/
>> >
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>> >
>> >
>> >
>> >
>> > --
>> > Jonathan Ellis
>> > Project Chair, Apache Cassandra
>> > co-founder of Riptano, the source for professional Cassandra support
>> > http://riptano.com
>> >
>> >
>>
>>
>>
>> --
>> Jonathan Ellis
>> Project Chair, Apache Cassandra
>> co-founder of Riptano, the source for professional Cassandra support
>> http://riptano.com
>
>



-- 
Jonathan Ellis
Project Chair, Apache Cassandra
co-founder of Riptano, the source for professional Cassandra support
http://riptano.com

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