Hi Mike, I'm not sure about all your questions, however you should take a look at LOCAL_QUORUM for your question about consistency level reads/writes.
2012/7/3 Michael Theroux <mthero...@yahoo.com> > 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 > > > > -- With kind regards, Robin Verlangen *Software engineer* * * W http://www.robinverlangen.nl E ro...@us2.nl Disclaimer: The information contained in this message and attachments is intended solely for the attention and use of the named addressee and may be confidential. If you are not the intended recipient, you are reminded that the information remains the property of the sender. You must not use, disclose, distribute, copy, print or rely on this e-mail. If you have received this message in error, please contact the sender immediately and irrevocably delete this message and any copies.
