Minecraft wiki entry for Shulker_farming, associated text: Another key consideration is 2-dimension (2D) versus single dimension (1D) farms. 2D farms make use of portals, which are a highly effective way of removing shulkers from the region around the breeding shulker, and also provide for a large number of teleportable spaces (with relatively few blocks). However, 2D farms can only be built in the overworld, meaning a shulker has to be transported from the end through the main portal gateway. Additionally, portal-based farms can often be unsuitable for busy servers, and diagnosing portal-linking issues can be a headache for less technical or less experienced players.