Hi Alex, Can you share what replication factor you're running? And, are you using ephemeral disks or EBS volumes?
Thanks! - Dan On Jul 3, 2012, at 5:52 PM, Alex Major wrote: > Hi Mike, > > We've run a small (4 node) cluster in the EU region since September last > year. We run across all 3 availability zones in the EU region, with 2 nodes > in one AZ and then a further node in each AZ. The latency difference between > running inside of and between AZ's has been minimal in our experience. > > It's only when we've gone cross-region that there's been latency problem. We > temporarily ran a 9 node cluster across 3 regions, however even then using > local quoram the latency was better than the standard datacenter - datacenter > latency we're used to. > > EC2Snitch is definitely the way to go in favour of NTS in my opinion. NTS was > a pain to get setup with the internal (private) IP address setup, so much so > that we never got it safely replicating the data as we wanted. > > Alex. > > On Tue, Jul 3, 2012 at 2:16 PM, Michael Theroux <mthero...@yahoo.com> wrote: > Hello, > > We are currently running a web application utilizing Cassandra on EC2. Given > the recent outages experienced with Amazon, we want to consider expanding > Cassandra across availability zones sooner rather than later. > > We are trying to determine the optimal way to deploy Cassandra in this > deployment. We are researching the NetworkTopologyStrategy, and the > EC2Snitch. We are also interested in providing a high level of read or write > consistency, > > My understanding is that the EC2Snitch recognizes availability zones as > racks, and regions as data-centers. This seems to be a common configuration. > However, if we were to want to utilize queries with a READ or WRITE > consistency of QUORUM, would there be a high possibility that the > communication necessary to establish a quorum, across availability zones? > > My understanding is that the NetworkTopologyStrategy attempts to prefer > replicas be stored on other racks within the datacenter, which would equate > to other availability zones in EC2. This implies to me that in order to have > the quorum of nodes necessary to achieve consistency, that Cassandra will > communicate with nodes across availability zones. > > First, is my understanding correct? Second, given the high latency that can > sometimes exists between availability zones, is this a problem, and instead > we should treat availability zones as data centers? > > Ideally, we would be able to setup a situation where we could store replicas > across availability zones in case of failure, but establish a high level of > read or write consistency within a single availability zone. > > I appreciate your responses, > Thanks, > -Mike > > > >
