Good advice for saving electricity in the server room

Server room power consumption represents a large proportion of the total consumption of electricity in office buildings. Thus, significant savings can be achieved by focusing on the server room – with consumption often decreasing by 30–50 per cent. The following pages offer some advice for saving electricity in the server room.

Saving electricity is a high priority in offices and other work places – for example, through the purchase of flat screens and notebook computers, and by focusing on lighting. But not much thought goes into power consumption in the server room, where the emphasis is on security and uptime.

In fact power used in the server room represents a large proportion of the total consumption of electricity in office buildings – about 200 GWh per year, a third of which is used for cooling (air conditioning) the server room.

Thus, significant savings can be achieved and, as demonstrated by a pilot project run by the Danish Electricity Saving Trust, server room power consumption can actually be halved (see www.serverrum.sparel.dk).

Substantial savings can be made by choosing powerefficient IT equipment. In addition, the need for cooling can be reduced if power consumption, and thus heat load, is reduced. Simultaneously, the server room should be efficiently located and laid out, and free cooling and a good cooling system installed.

The following pages offer practical advice for saving electricity in the server room under various headings:

Location of the server room

To minimise the need for cooling, the server room should be located in an unheated part of the building that offers the best possible thermal loss. Therefore the following should be noted:

• The server room should not have east, south, or west-facing windows to prevent ingress of the sun's warmth. Windows facing these directions must be fitted with heavy-duty blinds
• The server room should not be adjacent to a room with a high temperature – a boiler room for example
• The server room should have high thermal loss surfaces – for example, a large uninsulated north wall – or be located in a basement room with uninsulated walls and floors
• The server room should not be located in too small a room, because the temperature in a small room rises very quickly if the cooling system fails
• The server room should not be used as a storage area.

Servers, disk drives and power supplies

It is important to utilise the most energy-efficient IT equipment available. Devices not in use can also be switched off – for example, application servers not required outside normal working hours, and back-up units.

Uninterruptible power supplies (UPS) that ensure orderly shutdown in the event of a power failure consume very high levels of power. UPS efficiency should be greater than 90 per cent in relation to the actual output required.

Power supplies to servers, disk drives and the like are often not particularly efficient – frequently 50 per cent or less in the normal working environment. This means that half the energy consumed is wasted, and in addition this has to be 'cooled' away, which increases the electricity required to power the cooling system. It is difficult to establish the efficiency of power supplies but when commissioning new equipment users should definitely stipulate that these be at least 80 per cent efficient, or preferably over 90 per cent in a normal working environment for IT equipment.

When undertaking consolidation of servers – i.e. when combining many virtual servers onto fewer servers (Fig. A) – the number of servers can be reduced, which thereby also decreases the power consumption required to run the applications. The number of disk drives can also be reduced by aggregating the disk capacity in a so-called Storage Area Network (SAN) solution, where servers share the total disk capacity (Fig. B). In most cases this will lead to a reduction in power consumption to servers and disks of between 20 and 35 per cent.