On Thu, Aug 9, 2018 at 3:46 AM srinivasarao daruna <sree.srin...@gmail.com> wrote:
> Hi All, > > We have built Cassandra on AWS EC2 instances. Initially when creating > cluster we have not considered multi-region deployment and we have used AWS > EC2Snitch. > > We have used EBS Volumes to save our data and each of those disks were > filled around 350G. > We want to extend it to Multi Region and wanted to know the better > approach and recommendations to achieve this process. > > I agree that we have made a mistake by not using EC2MultiRegionSnitch, but > its past now and if anyone faced or implemented similar thing i would like > to get some guidance. > > Any help would be very much appreciated. > Hello, As we did this successfully in the past, here are some notes from the field: - configure the client applications to use address translation specific to EC2 setup: https://docs.datastax.com/en/developer/java-driver/3.3/manual/address_resolution/#ec2-multi-region - either specify the 'datacenter' name the client should consider as a local in the DCAwareRoundRobinPolicy() or provide private IP addresses of the local DC as contact points. This should ensure that the clients don't try to connect to the new DC which doesn't have the data yet. - review the consistency levels the client uses: use LOCAL_ONE and LOCAL_QUORUM instead of ONE/QUORUM for reads and writes, use EACH_QUORUM for writes when you want to ensure stronger consistency cross-region. - switching from plain EC2Snitch to EC2MultiRegionSnitch will change node's broadcast address to its public IP. Make sure that other nodes (in the same region and remote region) can connect on the public IP. Hope this helps, -- Alex
