It is point in time (time at which distcp runs). It can be automated using scripts. It is replication because you are replicating data. you are confusing replication with real time replication. Replication doesn't have to be real time. And it is impossible because of physics that any change in data in one cluster (or anyother database) will be reflected in the other. I'll give you the example of my HBase use case. We were using Active-Active replication. But even then, we knew that there might be a situation where data will be written to one data center and a power failure will occur as data is being replicated to the remote data center and some data will not be replicated (let's say up to 10 to seconds of data). The only other way to make sure that this does not happen is to "Ack" only when data has been written to the remote data center. This slows down every write and we had 10's of thousands of writes per second. See, you have to make a choice. If you would like to have 100 percent sync then you have to make sure that you ack every single record being written slowing down all your writes. Or you can do asynchronous replication which works 99.99% of the time but in case of network issues between two data centers, you know some data some time will not be replicated right away. There is absolutely nothing technology can do anything here. This is simple Physics.
... View more
