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From Harold Lim <rold...@yahoo.com>
Subject Re: Question about cassandra (replication)
Date Thu, 25 Jun 2009 15:10:56 GMT

Hi,

Is the replication factor configurable? For example, Can I configure the replication factor
per column-family (e.g., 5 for column-family a and 3 for column-family b).

Also, I am interested about the replication details. Sandeep wrote:
"When there's a failure and the #of replicas for a given key goes down,
Cassandra does not aggressively create a new copy for the data. The
assumption is that the failed node will be replaced soon enough, and work
can continue with the other 2 replicas."

When and how does cassandra replicate when the replication count of a particular data goes
below the replication factor? How does it monitor the replication count of a particular data?


-Harold






--- On Thu, 6/25/09, Jonathan Ellis <jbellis@gmail.com> wrote:

> From: Jonathan Ellis <jbellis@gmail.com>
> Subject: Re: Question about cassandra (replication)
> To: cassandra-user@incubator.apache.org
> Date: Thursday, June 25, 2009, 10:17 AM
> Rather than post the same question
> verbatim, it would be more useful
> if you explained what you still don't understand after
> Alexander and
> Sandeep's explanations on the google group.
> 
> (http://groups.google.com/group/cassandra-user/browse_thread/thread/4330e415e959e9d9)
> 
> On Thu, Jun 25, 2009 at 9:11 AM, Harold Lim<rold_50@yahoo.com>
> wrote:
> >
> > Hi All,
> >
> > I posted a similar message on the google groups page.
> Hopefully, I'll get more feedback here.
> >
> >
> > I just started reading about dynamo and Cassandra and
> I am thinking
> > about possibly using cassandra for my system.
> >
> > I was reading the dynamo paper and they mentioned
> about a preference
> > list for a particular key. Is this preference list
> configurable?
> >
> > How does Cassandra choose which nodes are in the
> preference list?
> > Also, are the number of replica for each key/column
> configurable? For
> > example, can I set the replication factor per
> key/value?
> >
> > I read that Cassandra has optimistic replication. What
> exactly does
> > that mean? Underneath the hood, how does cassandra
> maintain/detect the
> > number of replicas? Does it aggressively replicates an
> item, when it
> > detects that the number of replica of a particular
> item goes below the
> > specified repliation factor?
> >
> > Is the replication strategy (when to replicate,
> aggresiveness, etc)
> > configurable too?
> >
> >
> >
> >
> >
> >
> > Thanks,
> > Harold
> >
> >
> >
> >
> 


      

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