From what i understand emulating Horizons is next to impossible without some top of the line server hardware and resources. Shame, i think this game would do very well emulated.
Here is a thread where we were discussing this on another forum...The rest that follows is quotes from that forum by others. I am no expert by far, just dabbled in running some stuff here and there.
Aviendeha
"Here is the information about server specs for the Horizons shards, as told by Amon Gwareth on another forum:"
Amon Gwareth:
Current server runs on Xeons. not sure about a Woodcrest. Most ram you'd need would be 4gb per server box. Harddrive needs are negligible as its all database driven. You would need a database server, I have no idea what their requirements are or how many you'd need. The big costs are of course, the servers themselves up front and then the power, cooling and especially bandwidth.
Amon Gwareth:
You cannot get the footprint down to 2-3 servers. Not if you want monsters enabled and more than 10 players online at a time.
As for why you need such a powerful server farm to run a Horizons shard, another poster by the name of Dangit (Who used to be the lead moderator for Tazoon.com, and later for the main community site run by Tulga) posted this in the same thread:
Dangit:
The original server code was written to make heavy use of the ram. And at the time was hitting against the 2GB (or maybe 4GB) ram limit that MBs and OS had at the time. To make use of more ram than that, the server code has to be rewritten. The server uses a lot of memory.. 15MB per character 1.5 per other entity. An Entity is anything the player interacts with. Monster, resource node, machine etc. (I believe those numbers are correct) Then you have all the memory taken up by other aspects. From my own experience what I have found is you need 3 Servers with at least 2.0GHz Xeons, 4GB ram 60GB hard drives. And a database raid server with about 80GB.
That would be able to support about 150 people with enough monsters and resource spawning to keep some people happy. But your map size would be about the size of Lesser Aradoth.
Increase your land size and you will be adding another server. Otherwise performance becomes too erratic