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From Ted Dunning <ted.dunn...@gmail.com>
Subject Re: zookeeper cluster spanning datacenters
Date Thu, 22 Sep 2011 15:27:46 GMT
One additional architecture that has been proposed for people with only 2
data centers is to put 2+2 machines in the data centers and then put a tie
breaker in EC2.

On Thu, Sep 22, 2011 at 8:03 AM, Fournier, Camille F. <
Camille.Fournier@gs.com> wrote:

> We spread our ZKs across 3 data centers and in fact, these data centers are
> split across global regions (2 or 4 in one region, one in a remote region).
> To keep throughput up (and note that the throughput you have to worry about
> is only write throughput), we always ensure that the master is in one of the
> "local" data centers.
> If you have a very write-heavy and write time sensitive load, this might
> affect your performance. It won't affect reads at all because reads are
> serviced from the memory of the zk you connect to. For a mostly
> read-intensive load, splitting across data centers is unlikely to cause you
> problems.
> There is one exception: Monitoring. Even across data centers in the same
> region, we sometimes see zk dashboard unable to properly monitor the leader
> of a heavily-utilized cluster. This is due to the way the 4lw connections
> are managed, and something I'm trying to fix.
> If you have the machines to test, I would recommend running zk-smoketest  (
> https://github.com/phunt/zk-smoketest) on the proposed config.
> C
> -----Original Message-----
> From: Damu R [mailto:damu.devnull@gmail.com]
> Sent: Thursday, September 22, 2011 10:50 AM
> To: user@zookeeper.apache.org
> Subject: zookeeper cluster spanning datacenters
> Hi,
> I would like to know the downsides of having a zookeeper cluster that spans
> multiple datacenters. The requirement is a datacenter failure should not
> bring down the zookeeper cluster. From my understanding it is not possible
> to have a hot/cold cluster kind of setup possible. So we are thinking of
> putting zk servers in 3 colos(1+1+1 or 2+2+3). One of the major drawback I
> could think of is the throughput of the system affected by latency. The
> system does not require high throughput and can accept some latency. How
> much effect will the latency have on the throughput of the system? What are
> the other downsides of spreading the cluster across datacenters?
> Regards
> Damu

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