Home | About | Sematext search-lucene.com search-hadoop.com
NEW: Monitor These Apps!
elasticsearch, apache solr, apache hbase, hadoop, redis, casssandra, amazon cloudwatch, mysql, memcached, apache kafka, apache zookeeper, apache storm, ubuntu, centOS, red hat, debian, puppet labs, java, senseiDB
 Search Hadoop and all its subprojects:

Switch to Plain View
Zookeeper >> mail # user >> question about data replication


+
Brian Tarbox 2012-11-06, 14:50
+
Ted Dunning 2012-11-06, 16:37
Copy link to this message
-
Re: question about data replication
Ted,
Thanks. Is it an actual value I set in zoo.cfg or is it just implied by the
number of nodes in my cluster?
Sorry for being dense :-)

Brian
On Tue, Nov 6, 2012 at 11:37 AM, Ted Dunning <[EMAIL PROTECTED]> wrote:

> You specify the MINIMUM number of copies when you define the number of
> nodes in your ZK cluster.
>
> The idea is that ZK requires strong consistency and provides guarantees to
> that effect.  The only way to provide those guarantees is if a majority of
> the ZK cluster agree to and persist all changes.  That is in strong
> contrast to Cassandra which tries to provide availability instead of
> consistency.
>
> Since ZK requires a majority for every commit, a cluster defined with N
> nodes will require ceiling((N+1)/2) nodes to commit every change.
>  Likewise, N is not flexible without some care to make sure that these
> guarantees are maintained.
>
> On Tue, Nov 6, 2012 at 6:50 AM, Brian Tarbox <[EMAIL PROTECTED]>
> wrote:
>
> > I'm working with both Cassandra and Zookeeper so please excuse me if this
> > is a dumb question but does Zookeeper allow/require me to specify the
> > number of copies of data (like Cassandra does) or is it simply the case
> > that if a majority of nodes are up then ALL of my data is available?
> >
> > Thanks.  I'm guessing this should be obvious to me but searching the
> > various docs didn't yield a clear answer.
> >
> > Thanks again.
> >
> > Brian Tarbox
> >
> > --
> > http://about.me/BrianTarbox
> >
>

--
http://about.me/BrianTarbox
+
Ted Dunning 2012-11-06, 18:29
NEW: Monitor These Apps!
elasticsearch, apache solr, apache hbase, hadoop, redis, casssandra, amazon cloudwatch, mysql, memcached, apache kafka, apache zookeeper, apache storm, ubuntu, centOS, red hat, debian, puppet labs, java, senseiDB