Leading Environmental Threats in the Data Center

1. High operating temperatures in plenum spaces; above the plenum and in front of racks on cold aisles; inside IT racks, especially if fully enclosed, affect assets. ASHRAE recommends between 18°-27 C° or 64° - 80° F for data center temperatures.

2. Humidity affects assets. Low humidity leads to electrostatic discharge (ESD), damaging electrical components. High humidity causes condensation. ASHRAE recommends between 40% - 55% for data center humidity.

3. Water or fluid can damage electronic systems and cabling.

4. The position of rack doors and room doors directly relates to air flow/cooling and access control.  

5. Air Handler or CRAC Failure can jeopardize data centers. Not all have network monitoring and management capabilities, particularly older units. 

Sensor Placement Best Practices
A colleague who runs the IBM Green Data Center in Austin, Texas says it best: "Intelligent data allow for intelligent decisions."  Environmental monitoring solutions provide the infrastructure to collect intelligent data. 

Temperature Sensors
Data center design, load, capacity, percent utilization, efficiency goals influence the quantity/location of temperature sensors. 

For cold and hot aisles, sensor quantity varies, depending on goals and budget.  For closed racks with doors, place sensors on the inside of the door.  For open racks without doors, convenience and secure mounting location matter most. 

A good location for open racks is the left or right side of the rack, without interfering with the equipment "U" space.  Mount sensors consistently from rack to rack, row to row.  Place additional temperature sensors in plenum spaces as needed.

Humidity Sensors
Typically, sensors are placed on cold aisles, fairly far apart.  Best practices range from minimal humidity sensor coverage, with one humidity sensor/row placed in the front of a rack in the middle of the row, to maximum coverage of one humidity sensor for every three racks placed in the rack front. Mount sensors consistently.

Liquid Sensors
Place liquid or leak sensors near potential leak sources, such as CRACs.  More sources may exist, so involve facilities to identify these.  Add more if your facility is in the basement or partially below ground level because of outside water seepage.

Door Position Sensors
Place door sensors on all doors providing access to the data center— even if an access control system is installed.  Place door sensors on the front and rear of racks.

Dry Contact Sensors
CRAC or air handler not monitored via SNMP needs a dry contact sensor attached.  Outdoor generators and UPS systems also typically have dry contact connection points.

Shortcomings of Traditional Environmental Monitoring Solutions
Some require an aggregation appliance in each rack, connected to wired sensors. Others dictate one aggregation appliance for a row or group of racks.  Sensors from each rack are cabled back to the one appliance, so there are cable connections between racks.  Installation requires disciplined cable management.

The cost is of a wired solution is substantial.  Assuming a typical appliance costs (all figures, USD) about $800.00 and each environmental sensor costs about $99.00, a 250 rack data center costs:

• $274,250.00 or $1,097.00/ rack, with one appliance and three sensors/rack
• $114,250.00 or $457.00/rack, with one appliance for every five racks and three sensors

Aggregation appliances are scale-limited, with a finite number of ports for external sensors.  Adding sensors requires more appliances. Expansion is restricted to appliance port availability.

Appliances consume valuable rack space and require power and Ethernet connections. 

Lastly, the cost to deploy a wired monitoring solution is high.  Assuming a rate of $100.00 per hour, 30 minutes to install an appliance and 15 minutes to install a wired sensor, costs for a 250 rack data center:

• $31,200.00, assuming one aggregation appliance and three sensors installed/rack. Total install time = 312 person hours or 39 person days.
• $21,200.00, assuming one aggregation appliance installed for every 5 racks and 3 sensors installed/rack. Total install time = 212 person hours or 26 person days.

Advantages of Wire-free Environmental Monitoring Solutions
With no wires to purchase, install and manage, wire-free solutions have significant advantages. Such solutions include:

• Small wire-free, battery-powered sensors
• Radio frequency (RF) receivers, accessible on the TCP/IP network, that collect sensor data
• Monitoring software collects sensor information from receivers

Not all wire-free sensor solutions are equal. They must have:

• Small, inexpensive wire-free sensors – not small boxes with  wired external sensors
• Minimum 3-year battery life, with replaceable batteries
• Long range, wire-free communications between sensors and RF receivers that work inside of racks with doors and sides
• Simple setup and configuration requiring no "special" radio communications skills

Wire-free sensor solutions typically feature one or more RF receivers in the data center, easily covering at least 2,000 square feet.

Placed on the IT rack, small sensors are simply "stuck" to the rack using adhesive. Deployment time is fast.

Wire-free solutions cost much less than wired ones: between $40.00 and $90.00.  RF receivers cost between $1,000.00 and $1,300.00.   The best wire-free solution RF receivers easily handle 2,000-4,000 sensors and cover thousands of square feet. 

Assuming an RF receiver costs about $1,000.00 and each sensor costs about $79.00, costs for a 250 rack data center:

• $71,750.00 (USD) or $287.00/rack, assuming one RF receiver covers about 20 racks (conservative coverage) and three sensors are installed/rack.
• $65,500.00 (USD) or $262.00/rack, assuming one RF receiver covers about 40 racks (typical coverage) and three sensors are installed/rack.

Wire-free means no consumption of valuable rack space: RF readers typically mount to the ceiling. There's a very high sensor-to-RF receiver ratio, enabling massive scalability.

New sensors are added without wiring connections and cabling restrictions.

More than one RF receiver can receive the RF broadcast from each sensor.  Having multiple RF receivers with the same coverage zone eliminates the single point of failure of aggregation appliances.

Above all, wire-free is cheaper to deploy. Assuming a rate of $100.00/hour, 30 minutes to install a receiver and 5 minutes to install a sensor, estimates for a 250 rack data center:

• $6,800.00, assuming one RF receiver covers about 20 racks (conservative coverage) and three sensors are installed/ rack.  Total install time=68 person hours or 8.5 person days.
• $6,500.00, assuming one RF receiver covers about 40 racks (typical coverage) and three sensors are installed/ rack. Total install time=65 person hours or 8.2 person days. 

Environmental Monitoring Software "Must Haves"
As important as sensors, environmental monitoring software turns data into valuable, usable information. The software must:

• Scale to handle 10,000's of sensors
• Have sensor location as the primary attribute with sensor readings the secondary attribute. Data is useless without knowing the exact location of each sensor.
• Have centralized policy-based thresholds for simplified management and "mass management"
• Feature multiple notification methods for threshold breaches
• Be open for easy integration with enterprise class monitoring solutions.

Conclusion
Wire-free solutions are cheaper, easier to deploy, save critical rack space, provide massive scalability and future expansion and match today's "green data center" initiatives.

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