Feng Shui, the ancient art of using energy flows in natural and built environments for positioning, is gaining popularity in interior home decor. According to its dictates, the home PC should be facing east, south-east, or south, depending on the user's goal. East is associated with becoming busy, enthusiastic, and focused; south-east is linked to imaginative energy; and south relates to getting noticed.
Whether or not you buy into this theory for the home is up to you. When it comes to server room layout, however, there are sound, often energy-related, principles that should always be followed.
Down the Aisle
The separation of hot and cold air reduces hot spots, increases fault tolerance, and significantly reduces electricity consumption. In the cold aisle, equipment racks are arranged face to face. In the hot aisle, they are back to back.
Don't waste time trying to cool the hot aisles. The air there is supposed to be hot.
"It is a well known fact that facing all rows in the same direction causes each row to be fed hot exhaust air from the row in front of it, leading to overheating and dramatically reduced air conditioner performance," said Russell Senesac, director of InfraStruXure Systems at APC.
Don't waste time trying to cool the hot aisles. The air there is supposed to be hot. Instead, channel the hot exhaust so it stays separate from the cool equipment intake air, and focus on getting hot air efficiently back to the air conditioning system.
Stacking the Racks
Racks are more than mechanical support. They serve an essential function as part of the cooling system. The best rack designs prevent exhaust air from reaching equipment intakes, provide proper ventilation and space for cabling without airflow obstruction, and allow high-density supplemental cooling equipment to be retrofitted where necessary.
Proprietary racks are okay in some situation, for example, if the server room is a 100-percent HP or Sun shop. Otherwise, vendor-neutral racks usually mean lower cost, universal compatibility, and pre-engineering, which simplifies the planning process.
In addition, most server and storage manufacturers recommend blanking panels be used, as they prevent hot exhaust air from returning to the equipment intake. This reduces the likelihood of hot spots and increases equipment life
Blade in the Shade
Now that the blade honeymoon is over, smart admins have realized they can't cram hundreds of blades into a small space with impunity.
"Low-end vendors will try and sell a rack full of compute blades, which run incredibly hot," said Clive Longbottom, service director of business process analysis at Quocirca, an IT analyst firm in England. "A blade rack needs to be a complete compute system on its own."
This means it needs power supplies, storage blades, bandwidth, and pretty much anything else a standard server requires. By positioning these elements correctly, it is possible to minimize the amount of cooling required.
Blade density isn't the only cause for concern. Concentrating high-power loads in one location compromises the operation of those loads and typically increases operating costs. In addition, fault tolerance in the air delivery system can be compromised when high-power loads are concentrated.
Raise the Floor, not the Roof
While raised floors are commonplace, their effectiveness leaves room for improvement. For example, perforated tiling in the raised floor of the cold aisles enables cold air to be drawn into the face of the equipment. This cold air washes over the equipment and is expelled out the back into the hot aisle. Tiles with larger openings for improve airflow are available.
"By raising the height of the raised floor, airflow can be increased by up to 50 percent," said John Schmidt, ADC's product manager for Ethernet Infrastructure.
APC's Senesac suggests using gaskets or brushes on all under-rack wire openings in raised floors.
"This enables raised floor air distribution systems to deliver cool air to the equipment intakes located on the front of the racks," he said. "Openings below the racks feed cool air to the equipment exhaust, bypassing the equipment and reducing the performance of the cooling system."