Sitecore farm env
From what I can see Coveo creates a separate index for each server in a farm. I don't understand why it is setup this way, shouldn't all servers share the same index, this way index data is always in sync amongst servers.
Is it possible to have a single index for multiple servers? Also, I'd like to have it setup so I don't have to fiddle with index security everytime I add a new server to the farm.
Coveo can easily have a single index for multiple servers. You can install it on a server and make all your Sitecore instances point to it, just as described here : https://developers.coveo.com/display/SC201501/Installing+Coveo+for+Sitecore+on+Multiple+Hosts (you may want to read the two articles).