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. < [email protected]> 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:[email protected]] > Sent: Thursday, September 22, 2011 10:50 AM > To: [email protected] > 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 >
