1 Reply Latest reply: Jul 15, 2014 4:30 AM by user13061090 RSS

    Can you cluster Coherence over data centers?

    2644841

      We're currently running two separate Coherence clusters in different data centers. One is prod, the other DR.

       

      Would it be possible to cluster the nodes from each of these to create one cluster spanning both data centers? Then in a failover scenario the data would already be available.

       

      I know Coherence nodes heartbeat to one another to retain cluster membership and that there is a TTL setting to determine packet life. Would have nodes in different data centers result in heartbeats being missed or TTLs killing packets?

       

      Has anyone had any success with this?

        • 1. Re: Can you cluster Coherence over data centers?
          user13061090

          Coherence performance is related to the latency between nodes. Having one cluster spread over 2 data centers could harm performance (some timeouts could have to be changed to prevent nodes from data center A to claim another node in datacenter B is out of reach/possibly dead).

           

          When you lose network connectivity between the 2 data centers (note i'm not saying "if you lose connectivity". It WILL happen), you're welcome into the "split brain world", each half of the grid believing the other is dead and claiming to be the "master". And thus, if you have data replicated on N nodes, the master/backups are redispatched all over each datacenter, harming performance for a few minutes (the timing depending of course on many parameters...). And of course the data will no longer be synchronized between the 2 data centers. The quorum has to be thought of, and stuff like that...

           

          I might be wrong, but AFAIK I'd rather have 2 separate clusters. I believe 12.1 has new features to replicate data the the master grid to the DR one, I have not been through all the new documentation.