Welcome to the #chunkloading page, we are using @Railcraft anchors, they are on the list of limited blocks, the limit is increasing with ranks and limited blocks can be checked with /bl list command.
All @Railcraft Anchors load 3x3 chunks area with anchor itself in the central chunk.
Personal Anchor using 1 ender pearl per hour and load world only when the player who is placed it is online.
World Anchor load world when server is online using chunkloader Coins, which we have ingame /menu for sell, or from /kits for ingame ranks.
Anchors save their current time left for world load when broken down and drop items which was in its inventory, also anchors disabled with redstone signal, this make them simple for automation.