Not really, holesail does not need relays or servers. The P2P network running behind Holesail is a closed network that people can not enter unless they know an existing peer.
By default there are three public nodes, Node is a known peer, and anyone can become a node.
Node = Relay = Server?
If your destination doesn’t have a domain or a public static IP address, some of the communication has to go through a middleman. Which is fine…
Node is a known peer that know a lot of other peers who's IP address we know and who will accept all connections. It is not a Relay and anyone can become a Node.
Check out Kademliya algorithm.