Dave Wolfenden asks why, although testing a data centre before the client takes possession is integral to its creation, few IT pros look at the testing procedures that could affect its reliability.
4 November 2014
Testing a data centre before handover to the client is a normal part of data centre construction, but few IT professionals look at the testing that is carried out that can affect modern centres in the future.
The usual reason for this is that until a full set of servers and allied IT systems are in place it is perceived as impossible to test a data centre under full loading conditions.
This assumption is incorrect, but it seems to be perpetuated by a number of misunderstandings about the complex technologies involved in a typical data centre.
In many cases airflow within the data centre is modelled using Computational Fluid Dynamics (CFD) modelling software during the design phase. In addition to the testing set out by the commissioning team the CFD model should be proved before the IT infrastructure is installed.
The data centre facility should be tested at a variety of load levels, working up to 100 per cent load. Most of the energy consumed by IT infrastructure is rejected as heat; the simplest way to replicate the IT infrastructure is the use of fan heaters.
The heaters are often connected to temporary power supplies. These types of load do not reflect the airflow and temperature range akin to IT infrastructure and do not test the power supply end-to-end.The
CFD model at 100 per cent is likely to assume that the data centre is fully occupied with floor standing and rack-mounted IT infrastructure. But during testing only some of the racks may be installed. To ensure the testing process is valid, temporary measures, such as installation of temporary IT racks, need to be in place to ensure the layout and load distribution reflect the CFD model layout.
Although the latter two issues can be met using sensible planning, effective heat control is something of a science in its own right, as dissipating heat - from whatever source - within the data centre is a critical process.
If carried out poorly or by using unreliable technology, a runaway heat problem can turn into an IT disaster, shortening both system and server lifespan at best - and causing equipment failures at worst.
ROI v cost conundrum
In an ideal world a business could throw enough money at a data centre project to make sure of 100 per cent uptime and happy customers, as well as staff. But in the real world, even in a mission-critical application, there are clear return on investment (ROI) issues that must be addressed when planning, testing and maintaining an effective facility. Corners may wrongly be cut when it comes to a process called Heat Load Testing, where the prodigious heat output of servers and allied IT systems in a data centre is emulated using specialist equipment such as a heat load bank or server emulator.
Although this testing equipment is cost-effective, the fact that the units have to be installed in a 'shell' data centre - that is, relatively complete apart from the IT systems and servers for several weeks and on a wide scale, has led some firms to superficially test the heat and electrical load, rather than apply in-depth testing processes.
A new IT equipment room, data centre - or modular data centre - is designed and expected to run continuously for the duration of its design lifetime, which can amount to years, even in the rapidly evolving IT arena.
Using actual servers to complete the tests is not possible, owing to the cost of filling the data centre with servers, the potential for damage to IT equipment and the time it would take to reset servers after each test.
Coupled with the need for fixed, predictable loading during testing, a server emulator provides a variable electrical load and produces a heat load. These loads allow the testing of the electrical and cooling systems in a controlled environment.
Test units in detail
Good testing equipment allows the thermal inspection of all joints and connections under a full load condition before the building becomes operational, so reducing the fire risk. One useful side effect of this process is that the electrical assessment process provides confirmation that power monitoring and billing equipment is operating correctly, as well as minimising risks and issues that may not otherwise be found for several years.
Allied to the electrical check process is the testing of ancillary systems such as electromechanical and mechanical units, pumps, cooling and chiller systems, as well as room air conditioning units (RACU) where appropriate. These tests are also useful for load testing of intermediate heat exchangers, which are usually installed to cut water leakage loss in the suite, with capacities ranging from 100,000 litres all the way down to 250 litres.
For water chilling, the testing process normally requires load testing to prove that the chilled water ring has a sufficient volume of cold water to allow the chillers to restart when a generator kicks in, so negating the requirement to UPS-equip the chillers for resilience.
All these methods are a fundamental aspect of data centre testing as the comprehensive checking of electrical and chilling/cooling systems is infinitely preferable - on several fronts - to destroying a bank of servers. A rack of heaters cost a few thousand pounds, against the cost of a rack of servers that can cost up to six figures.
By documenting a safe and reliable testing phase of a data centre deployment, this can act as proof to insurers that the systems are fit for purpose under full load, as well as providing full assurance that the components and systems are set up and configured correctly.
Dave Wolfenden, director of Mafi Mushkila