The Need For High Density Zones Efficient Datacentre Layout:
High-density equipment such as blade servers, 1U servers and multi-core high end servers offer more computing per watt than previous generations servers. The drawback is that every watt of power consumed is turned to heat, creating a cooling conundrum for datacentres housing both legacy, lower density servers alongside todays’ high density IT equipment. Fortunately the solution is simple - implement high density zones which support mixed density cooling requirements within a single data hall. By Paul Tyrer, VP North EMEA, APC by Schneider Electric.
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igh density zones act as a self- contained high-density datacentre within an existing low-density facility, thermally invisible to the rest of the
room. They work by isolating server exhaust heat and directing all that heat into the air-conditioner intakes, where the air is first cooled before being redistributed in front of the servers. By isolating both hot and cold air streams, thermal impact is neutralised so high density zones present a room neutral load to the existing datacentre cooling system. Placing high-density zones in an isolated, standardised and self-contained area of the datacentre also provides a low cost and viable solution to the unpredictable nature of legacy raised floor cooling methods. Additionally it would not require complex computational fluid dynamics (CFD) analysis of datacentre airflow prior to installation.
There are three types of high-density zone methodologies: Uncontained zones; Hot Aisle Containment Systems (HACS); and rack air containment.
Uncontained zones rely on the standard layout and widths of the common hot aisle and cold aisle arrangement to keep hot and cold air streams from mixing. This method is best used when IT racks designated for the zone are moved and relocated frequently and when racks are
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used from a variety of different vendors. Uncontained zones depend on multiple racks in a row are not effective in cooling stand alone IT racks. The closer an IT equipment rack is to a row-based air conditioner, the greater the amount of exhaust air that is being captured and cooled. As greater the distance between the IT racks and the row-based air conditioner, the more the hot air mixes with surrounding air in the datacentre. Plus more row-based air conditioners required at lower densities to properly capture hot exhaust air from IT racks. With Hot Aisle Containment the hot aisle in every pair of rows is contained, and becomes the hot exhaust channel by enclosing it with ceiling panels and a door at the end of the aisle. In addition, the racks’ rear doors are removed. The hot exhaust air is physically contained and unable to mix with the ambient datacentre air. A wall or another row of racks is required to form a cold aisle in order to isolate the cold supply air.
This method is best applied in areas where floor space is at a premium and is popular because it consumes the same space as two rows of low density racks. It’s also good in datacentres with hot and cold aisle layouts. HACS with a row-based cooling architecture are considered to be more efficient, more flexible, provide
better ride through capability and offer a way to better address the need to manage higher density requirements without making the entire datacentre hotter than necessary.
Rack containment is similar to hot aisle containment except that the hot exhaust air is contained using the back frame of the equipment racks and a series of panels to form a rear air channel – this can be attached to a single IT rack or to a row of racks. An optional series of front panels may be used on rack containment arrangements that require complete containment of hot and cold air streams. Architectures such as row-based cooling and hot aisle containment allow for the rapid deployment of high-density zones within an existing or new low density datacentres. Rather than having a datacentre specified to cool one power density, modular row-orientated cooling and power can be added where and when high density racks are required, without any effect on the existing room-level infrastructure. In combination with capacity and change management systems, high density zones offer a solution capable of maintaining a room- neutral and predictable operation even after moves, additions and changes to the IT load. Tel: 0800 2799254
www.apc.com
Building & Facilities Management – November 2010
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