Electromagnetic Interference in the Data Center: To Shield Or Not To Shield
Jordi Ferri, Shielding, Power & Cooling Division Manager, Advanced Shielding Technologies Europe S.L. (AST), Barcelona, Spain
When designing a data center, many things need to be taken in account. One of them is availability and downtime depending on desired Tier configuration (see Table 1). For Tier III and Tier IV data centers, apart from redundancy of the elements, there are potential threatens and design rules that need to be considered to avoid future unexpected incidents and assure up-time of the systems hosted inside.
Low and High frequency electromagnetic fields interference (EMI) caused by power equipment, cell phones, microwaves, TV and radio signals, etc. can produce harmful effects on IT equipment, thus reducing quality of service and availability. EMI is usually ignored when designing a data center; the following article will discuss some reasons why EMI, though invisible, may produce serious visible effects and why protection measures need to be taken.
DATA CENTER ENVIRONMENT
An ideal data center location is one that offers many of the same qualities that a data center itself provides a company:
Protection from hazards
Features that accommodate future growth and change
Site Risk Factors
Every parcel of land comes with unique hazards. Knowing the hazards associated with any property upon which you consider placing a data center is very useful and should be a serious consideration.
Regardless of whether the dangers are naturally occurring or man-made, it helps to understand how they can affect a server environment, how to alter your data center’s design to prepare for them.
Electromagnetic interference, or radio frequency interference, is when an electromagnetic field interrupts or degrades the normal operation of an electronic device. Such interference is generated on a small scale by everyday items ranging from cellular phones to fluorescent lights. Large sources of interference, such as telecommunication signal facilities, airports, or electrical railways, can interfere with data center servers and networking devices if they are in close proximity.
System administrators, network engineers, and others who work directly with the equipment are most likely to see symptoms first, even if they don’t realize their cause. If you learn of a server experiencing unexplained data errors and standard troubleshooting doesn’t resolve the problem, check around for possible sources of electromagnetic interference.
High levels of EMF will have disastrous effects on computer equipment, servers, CRT screens, medical equipment and other electronic devices. The results can be anything from shaky monitor screens to intermittent and unexplained failures. Electronic magnetic frequencies are all around us. In office buildings the frequencies can be generated by high power lines, transformers, UPS equipment and high voltage switch gear and these sources may be hidden in walls or behind doors where no one is suspect.
AST has developed and supplies many different shielding products—coatings, compounds, and metals; meshes, strips, and even metalized fabric— that are available to block electromagnetic interference.
Effects in Communications Cabling
When cable is in close proximity to strong electromagnetic fields, unwanted current and voltage may be induced on it. If the power level is high enough, the electrical “noise” can interfere with voice and data applications running on the cabling. In data communication, excessive electromagnetic interference (EMI) hinders the ability of remote receivers to successfully detect data packets. The end result is increased errors, network traffic due to packet retransmissions, and network congestion. For analogue voice communication, EMI can create psophometric noise, which degrades transmission quality.
Capacitive coupling occurs between power and telecommunications cables carried in parallel for some extent in a given installation. Power cable shielding can be employed to shield the channel from the disturbing circuit.
Inductive coupling occurs via the mutual inductance between two or more circuits or channels. When current flows in a circuit terminated with a load, it produces a magnetic flux proportional to the current. This magnetic flux may induce noise voltage into an adjacent channel, generating a loop current in the disturbed circuit. This type of coupling is one of the most common. The geometry of the conductors, as well as the geometric range between two lines in space, determines the intensity of the inductive coupling. Another important factor is the environment that contains the lines. For example, metallic raceway or cable tray can help attenuate or propagate unwanted signals beyond the initial source of interference.
In order to reduce the effect of inductive coupling between circuits, it is important to maintain cable geometry along the entire channel length and to keep adequate separation between circuits. The intensity of the magnetic field is directly proportionate to the current present in the disturbing channel and inversely proportionate to the distance between the lines.
Protecting Cabling Systems Against EMI
While electromagnetic interference can affect the performance quality of structured cabling systems, EMI shielding is an effective method to help avoid this.
Shielding is one of the techniques employed to protect telecommunications cabling systems from EMI. When designing and installing shielded solutions, the grounding/earthing and bonding have to be very carefully considered. Proper grounding and bonding are mandatory to assure the effectiveness of shielded systems.
In case of not enough available separation between cables, it is possible to install shielded trays for power cabling (see Figure 2).
Effects in Hardware
Low frequency EMI caused by power sources can produce very harmful effects in hardware, p. e a hard disk can be easily erased just with the action of a close magnetic field.
Another reason for shielding is EMF attacks. The oldest cyber frontier is actual physical attack or the threat of attack to disable data centers. This can be done without saboteurs ever gaining access to the interior of the data center.
EMF: INFORMATION SECURITY
It has been reported that in some cases information technology equipment (ITE) such as personal computers leaks information via unintended electromagnetic waves radiated mainly from displays. Here, we assume that there are three main threats to information security from electromagnetic emissions and to immunity (Figure 3).
Leakage of information by electromagnetic emissions: Information is obtained from weak electromagnetic radiation from telecommunication equipment (including terminals).
Malicious attacks on immunity by high-power electromagnetic waves
Malfunctions or system crashes are caused by malicious exposure to HPEM.
The dangers of information leakage by electromagnetic emissions include:
unintentional emanations conveying image information emitted from the displays of information technology equipment, such as PCs, and from laser printers, IC cards, and card readers and
exploitation of information in databases handled by servers at public key infrastructure (PKI) centers and financial data centers.
It has been reported that even if the level of such electromagnetic radiation is below the limits regulated by the Voluntary Control Council for Interference by Information Technology Equipment (VCCI), information can be obtained from the weak signals at some distance. As threats of malicious HPEM attacks on immunity, we consider the intentional irradiation of telecommunication equipment by HPEM from high-power transmitters, such as intentionally altered radio transmitters and radars (radio detection and ranging), microwave ovens, high-voltage apparatus for self-defense (e.g., tasers), and surge generators for testing. As a first step toward countermeasures against these electromagnetic information security problems, it is recommended to shield the datacenter accordingly to provide a high-security electromagnetic-radiation-shielded room.
ABOUT THE AUTHOR
Jordi Ferri heads the Shielding, Power and Cooling Division at AST, a firm specialized in Modular IT Physical Infrastructures, with a number of international patents in different innovations and with a presence in more than 20 countries. Jordi has 13 years of experience in mission critical and telecommunication infrastructures. Jordi is a Telecommunications Engineer from UPC University, holds a Master in Project Management from La Salle University in Barcelona and an MBA from ESADE Business School.
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