HI Chad,
 The maximum number of zookeeper servers we have tested with is 13. Even
with 13 the performance starts to degrade very quickly (compared to ensemble
of 5 and 7). I am not sure we have the current numbers (we have made 3x or
so performance improvements) but with the old number in zookeeper.pdf on
http://wiki.apache.org/hadoop/ZooKeeper/ZooKeeperPresentations

The slide is at the end.

You can see that the performance drops with 13 servers. We usually suggest 5
or 7 servers for ZooKeeper. We can get around 20K-30K writes per second and
more than 50K reads per second from an ensemble of 5 servers (as of now with
performance enhancements). With 5 servers you can tolerate a failure of 2
nodes. 
Please take a look at zookeeper presentations -
http://wiki.apache.org/hadoop/ZooKeeper/ZooKeeperPresentations
To find out more about Zookeeper.

What is the rationale behind having such a huge amount of zookeeper servers?

Thanks
mahadev


On 3/3/09 5:30 PM, "Chad Harrington" <charring...@datascaler.com> wrote:

> Clearly Zookeeper can handle ensembles of a dozen or so servers.  How large
> an ensemble can one build with Zookeeper?  100 servers?  10,000 servers?
> Are there limitations that make the system unusable at large numbers of
> servers?
> 
> Thanks,

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