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From Aaron Blew <aaronb...@gmail.com>
Subject Re: RackAwareStrategy Documentation Disparity
Date Fri, 11 Jun 2010 18:33:42 GMT
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
>

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