Green IT: data centre design

7.1. Measuring operational energy efficiency

One of the benefits of designing and building a green field data centre is the ability to include effective and useful instrumentation within the design at little additional cost.

Before spending additional money on metering equipment it is important to understand what benefits are expected from this instrumentation and the uses to which the data can be put. Many operators have installed expensive products that meter at the IT power strip or socket level in the data centre. Whilst per socket metering can provide very granular information this data is not directly useful to OUCS who do not charge occupants collocation fees including a multiple of metered power. As indicated in section 6.2.2 it is not reasonable or useful to allocate energy use or cost to a device based only on the metered power at the PSU, further, as technology advances and more devices are virtualised the notional relationship between a power socket and a logical server or service component is removed. Many IT devices also now report their energy use through management APIs (this is required in the new Energy Star for Compute Servers standard) which avoids the additional problems involved in associating a physical IT device with a numbered socket.

Whilst many operators have installed instrumentation to measure power within the data centre this is normally the energy used by the IT equipment and not the energy we are concerned with, the energy wasted by non-IT equipment. If this is measured at all it is frequently in Building Management Software and not visible to the IT department.

If the goal is to understand and manage IT energy use, energy efficiency and cost then a combination of IT and Mechanical and Electrical device consumption metering is required. PDU or rack level metering of the IT load is all that is necessary for OUCS when coupled with effective reporting of the data centre infrastructure loads.

Figure 5 illustrates three levels of data centre energy instrumentation. It is recommended for the OUCS CMR that at least the detailed measurement points (light blue) be instrumented. The meters should be network connected and able to log their data to a central station. Many BMS systems available today are able to accept logging data from remote energy meters. This data should be available from the BMS to other software. The historic reporting data should be stored in as granular a form as possible, at least hourly if not at the 300 second IT polling rate.

Data captured from the detailed measurement points will allow the simulation of future energy impacting changes and thus give a much greater understanding and control of energy management within the CMR.

7.2. Applying the EU Code of Conduct for Data Centres

It is recommended that Oxford University implement the EU Code of Conduct for Data Centre operators. The Code details best practices that apply to M and E infrastructure, IT systems and software. The best practices have been developed and reviewed by industry experts and represent a practical and effective approach to energy efficient design and on-going energy management within the data centre.

Romonet recommends that Oxford University implements the following best practices defined in the EU Code of Conduct for data centres at a minimum. Ideally Oxford University would become a full Participant of the code and report its energy data back to the EU under the requirements of Participant status. The mandatory requirement for reporting of high-level power data will ensure regular (six monthly) senior visibility of the energy data from the CMR and an increased understanding and appreciation of how the efficiency of the facility is being managed. Regular reviews of the reporting will also give a much better appreciation of the rate of growth in IT service related energy.

7.3. Service categorisation and grouping

The services delivered by OUCS should be reviewed to determine the required resilience and availability levels for each service. For user facing services (such as email) this is dependent upon the level of direct user impact from service failures whilst for infrastructure services (such as dns) this is determined from the impact upon user facing services (such as Internet access).

As OUCS will have multiple machine rooms and the ability to deliver multiple levels of resilience at the facility, hardware, network and software level it is sensible to define a series of standard offerings to meet the range of common availability criteria. The following table suggests a range of recovery and continuity levels and mechanisms as an example.

It should be noted that hardware level disk replication is only necessary for legacy applications that offer no higher level replication of data and should not be viewed as a strategic solution.

7.4. Service catalogue and CMDB

Many of the best practices identified above will be easier to achieve if a comprehensive Service Catalogue is implemented and maintained. Alongside the Service Catalogue, a Configuration Management Database should be established and rigorously maintained for the new CMR to ensure that existing IT equipment is both documented and controlled. All changes in location, connections, memory, storage etc. – i.e. “configuration” – should be recorded in detail in the CMDB.