How many nodes are you planning to add? How many replicas do you want? In general, there shouldn't be a problem adding nodes and then altering the keyspace to change replication. You will want to run repairs to stream the data to the new replicas. You shouldn't need downtime or data migration -- this is the beauty of Cassandra.
Sean Durity – Lead Cassandra Admin -----Original Message----- From: Ajay Garg [mailto:ajaygargn...@gmail.com] Sent: Wednesday, October 07, 2015 11:56 AM To: user@cassandra.apache.org Subject: Is replication possible with already existing data? Hi All. We have a scenario, where till now we had been using a plain, simple single node, with the keyspace created using :: CREATE KEYSPACE our_db WITH replication = {'class': 'SimpleStrategy', 'replication_factor': '1'} AND durable_writes = true; We now plan to introduce replication (in the true sense) in our scheme of things, but cannot afford to lose any data. We, however can take a bit of downtime, and do any data-migration if required (we have already done data-migration once in the past, when we moved our plain, simple single node from one physical machine to another). So, a) Is it possible at all to introduce replication in our scenario? If yes, what needs to be done to NOT LOSE our current existing data? b) Also, will "NetworkTopologyStrategy" work in our scenario (since NetworkTopologyStrategy seems to be more robust)? Brief pointers to above will give huge confidence-boosts in our endeavours. Thanks and Regards, Ajay ________________________________ The information in this Internet Email is confidential and may be legally privileged. It is intended solely for the addressee. Access to this Email by anyone else is unauthorized. If you are not the intended recipient, any disclosure, copying, distribution or any action taken or omitted to be taken in reliance on it, is prohibited and may be unlawful. When addressed to our clients any opinions or advice contained in this Email are subject to the terms and conditions expressed in any applicable governing The Home Depot terms of business or client engagement letter. The Home Depot disclaims all responsibility and liability for the accuracy and content of this attachment and for any damages or losses arising from any inaccuracies, errors, viruses, e.g., worms, trojan horses, etc., or other items of a destructive nature, which may be contained in this attachment and shall not be liable for direct, indirect, consequential or special damages in connection with this e-mail message or its attachment.
