As with any IT project, a little planning at the outset can prevent big headaches down the road. When you’re designing a data center, server room or network closet, deciding which racks to deploy and how to configure them should be at the top of your list. Once you’ve chosen the type and quantity of racks needed as well as the IT equipment such as servers and routers within each rack, you’ll need to come up with a plan to install the racks and equipment. Here are some things to consider while planning your installation.
Room Attributes
When choosing a room or considering an upgrade to an existing room, make sure you have enough space for all the racks you’ll need now and in the foreseeable future. And don’t forget that you need to move the racks from the point of delivery to the final location. Your facility’s doors must be tall enough, the floors must be sturdy enough and stairs should be avoided. The room’s circuits must provide the correct voltages and sufficient amperage for all your equipment. There must be a way for cables to enter and exit the room.
The room should be away from heat sources, whether they are inside or outside the building. And the room should have some way to get rid of the heat generated by your equipment. This may include heat dissipation through the walls and active or passive ventilation through ducts, raised flooring or dropped ceilings. Installations with higher wattage densities and heat production may also require dedicated computer room air conditioners (CRACs). Using “close-coupled” CRACs can increase efficiency compared to traditional perimeter CRACs.
Rack Layout
You should develop a blueprint for the placement of the racks in relation to the room, each other and important resources such as power circuits and cooling. Rack layout is especially important for cooling. Cooling will be more efficient and more effective if you prevent hot air from recirculating and mixing with the cold air supply. You should arrange rack enclosures in solid rows with hot aisles (where the racks are back-to-back) and cold aisles (where the racks are front-to-front). Arranging racks in a hot-aisle/cold-aisle layout can reduce energy use up to 20%. You should also “bay” rack cabinets by connecting them side-to-side. Baying creates a physical barrier between hot and cold air that discourages recirculation. Some enclosures include the baying hardware required to link them together.
Enclosures offer much more control over airflow. But even if you’re using open frame racks, or if you have too few racks for more than a single row, it’s important to pay attention to the arrangement of the racks. You should make sure the equipment in one rack isn’t drawing in hot air from the equipment in another rack, or from any other obvious heat source.
Equipment Placement
The location of equipment in the rack is vital to the proper operation of servers and other equipment, to maximize the space inside the rack and to permit easy service. You should develop a detailed plan for equipment placement before you install it, including plans for future expansion. Naturally, you need to make sure each rack has enough rack spaces to accommodate all the equipment you plan to install.
The weight of your equipment must not exceed the rack’s load rating. Always place the heaviest equipment, such as UPS systems and external battery packs, toward the bottom of the rack. This prevents the rack from becoming top-heavy and prone to tipping over—especially important if you plan to install equipment before rolling the rack to another location. (When rolling a rack, with or without installed equipment, you should always push it away from you—not pull it toward you. Push along its longest axis, which is almost always from front to back or back to front.) If sliding rails allow equipment to extend away from the rack horizontally, you should avoid placing this equipment too high in the rack. Also make sure it can’t extend so far that it unbalances the rack.
Consider factors such as cable management when deciding where to install equipment in the rack. For applications that require high-density cabling, you may need 1U of horizontal cable management for every 1U of patch panels or switches. And if you plan to install a rack console or console KVM, you’ll need to consider where the LCD monitor and keyboard will be at a comfortable height. You should also consider spreading blade servers and other high-density, high-wattage loads among multiple racks to prevent problematic hot spots.
