When people have multiple servers, often they need/want those servers to communicate. For example, I might have a web server and a separate database server. So anything on my web server that needs to make a database query would have to communicate over the network to the database server. Prior to this change, Digital Ocean users would have to do that communication over the public internet interface (public IPs), and the traffic would count towards their quota. Now, the servers can have private-side interfaces that aren't internet-facing, allowing this internal communication to take place on the internal network, avoiding the public interfaces and not counting towards the traffic quotas.
I'd also expect internal communication to be much faster than going over the internet.
Apparently this isn't the case:
| The latency is actually the same whether you traverse the public or private network because either way it won't get routed out to the edge and back.
the latency will be similar in un-congested conditions (it will stay inside the network edge) but private networks allow the switched network to broadcast less, allowing it to handle "more" traffic across switch backplanes and area networks.
Well, the nature of routing is such that, for communication between two VPS in a given datacenter, the traffic wouldn't really "go over the internet", but it ought to still help to have the internal traffic separated from the public side.
Say if you have 3-4 cache servers that need to talk to one another, rather than having to give it a public IP (even though it's not routed outside of DO), you can give it an internal IP so all traffic is routed through that network interface instead of the public one - slightly better for security though not perfect as everyone with a DO box can see your private network ip, so you still need to secure it.......
High availability setups. While the heartbeat inter-node communication is low bandwidth, it's unfeasible to run DRBD over a public interface.
hmm... are we still in hacker news?
Not everyone is born with intrinsic knowledge of systems administration. Deriding someone for attempting to expand their knowledge is disgusting and needs to stop.
You can be a hacker and still know nothing about how modern website backends are designed.
There are lots of people who hack electronics or do desktop programming who have no idea how servers work even though they might be interested. We can't know everything and reminding people of their ignorance when they're asking to know more is discouraging. Stop it.