Hi Amod, thank you for posting your question on Aerospike forum. Let me try and answer this for you.
Q1. The only overhead XDR will have on the source cluster is the extra read which it does while shipping the data to a remote cluster. There is no overhead on RAM/SSD. But since it is cross data center replication there will be overhead on the network, based on the amount of data you are replicating.
Q2. The number of XDR locations does not affect the parent cluster in any way, having said that this is true when links to all the destination clusters are up and running. But when there is a remote DC down situation, you will have that extra overhead of read on the source cluster. This is because Aerospike does not stop shipping to all DCs just because one DC is down.
Q3. It is not recommended and not a good idea to have destinations with large latency differences. XDR throughput will only be as good as your slowest destination.
If you have 8 DCs to ship to, then it’s better to have the source DC ship to the lower latency ones first, and then forward it to other DCs from there, you can configure XDR to do this automatically using “forward-xdr-writes” feature.
As a rule of thumb, having one source and too many destinations is not a good idea. Your network can be a bottleneck in this case. Hope this helps.