CIT 470: Advanced Network and System AdministrationSlide #1 CIT 470: Advanced Network and System Administration Data Centers

Topics Data Center: A facility for housing a large amount of computer or communications equipment. 1.Racks 2.Power 3.PUE 4.Cooling 5.Containers 6.Economics

Google DC in The Dalles Located near 3.1GW hydroelectric power station on Columbia River

Google DC in The Dalles

Inside a Data Center

Inside a Container Data Center

Data Center is composed of: A physically safe and secure space Racks that hold computer, network, and storage devices Electric power sufficient to operate the installed devices Cooling to keep the devices within their operating temperature ranges Network connectivity throughout the data center and to places beyond

Data Center Components

Data Center Tiers See for more details about tiers.

Racks: The Skeleton of the DC 19” rack standard –EIA-310D –Other standard numbers. NEBS 21” racks –Telecom equipment. 2-post or 4-post Air circulation (fans) Cable management Doors or open

Rack Units

Rack Sizes

Rack Purposes Organize equipment –Increase density with vertical stacking. Cooling –Internal airflow in rack cools servers. –Data center airflow determined by arrangement of racks. Wiring Organization –Cable guides keep cables within racks.

Rack Power Infrastructure Different power sockets can be on different circuits. Individual outlet control (power cycle.) Current monitoring and alarms. Network managed (web or SNMP.)

Rack-Mount Servers 4U 1U

Blade Servers

Buying a Rack Buy the right size –Space for servers. –power, patch panels, etc. Be sure it fits your servers. –Appropriate mounting rails. –Shelves for non-rack servers. Environment options –Locking front and back doors –Sufficient power and cooling. –Power/environment monitors. –Console if needed.

Space Aisles Wide enough to move equipment. Separate hot and cold aisles. Hot spots Result from poor air flow. Servers can overheat when average room temperature is too low. Work space A place for SAs to work on servers. Desk space, tools, etc. Capacity Room to grow.

Data Center Power Distribution power.htm

UPS (Uninterruptible Power Supply) Provides emergency power when utility fails –Most use batteries to store power Conditions power, removing voltage spikes

Standby UPS Power will be briefly interrupted during switch Computers may lockup/reboot during interruption No power conditioning Short battery life Very inexpensive

Online UPS AC -> DC -> AC conversion design True uninterrupted power without switching Extremely good power conditioning Longer battery life Higher price

Power Distribution Unit (PDU) Takes high voltage feed and divides into many 110/120 V circuits that feed servers. –Similar to breaker panel in a house.

Estimating Per-Rack Power

The Power Problem 4-year power cost = server purchase price. Upgrades may have to wait for electricity. Power is a major data center cost –$5.8 billion for server power in –$3.5 billion for server cooling in –$20.5 billion for purchasing hardware in 2005.

Measuring Power Efficiency PUE is ratio of total building power to IT power; efficiency of datacenter building infrastructure SPUE is ratio of total server input to its useful power, where useful power is power consumed by CPU, DRAM, disk, motherboard, etc. Excludes losses due to power supplies, fans, etc. Computation efficiency depends on software and workload and measures useful work done per watt

Power Usage Effectiveness (PUE) PUE = Data center power / Computer power –PUE=2 indicates that for each watt of power used to power IT equipment, one watt used for HVAC, power distribution, etc. –Decreases towards 1 as DC is more efficient. PUE variation –Industry average > 2 –Microsoft = 1.22 –Google = 1.19

Data Center Energy Usage

Sources of Efficiency Losses UPS –88-94% efficiency –Less if lightly loaded PDU voltage transformation –.5% or less Cables from PDU to racks –1-3% depending on distance and cable type Computer Room Air Conditioning (CRAC) –Delivery of cool air over long distances uses fan power and increases air temperature

Cooling a Data Center Keep temperatures within ◦ C Cooling equipment rated in BTUs –1 Watt = 3412 BTUH –BTUH = British Thermal Unit / Hour Keep humidity between 30-55% – High = condensation – Low = static shock Avoid hot/cold spots – Can produce condensation

Computer Room Air Conditioning Large scale, highly reliable air conditioning units from companies like Liebert. Cooling capacity measured in tons.

Waterworks for Data Center

Estimating Heat Load

Hot-Cold Aisle Architecture Server air intake from cold aisles Server air exhaust into hot aisles Improve efficiency by reducing mixture of hot/cold

Free Cooling Cooling towers dissipate heat by evaporating water, reducing or eliminating need to run chillers Google Belgium DC uses 100% free cooling

Improving Cooling Efficiency Air flow handling: Hot air exhausted by servers does not mix with cold air, and path to cooling coil is very short so little energy spent moving Elevated cold aisle temperatures: Cold aisle of containers kept at 27 ◦ C rather than ◦ C. Use of free cooling: In moderate climates, cooling towers can eliminate majority of chiller runtime.

Server PUE (SPUE) Primary sources of inefficiency –Power Supply Unit (PSU) (70-75% efficiency) –Voltage Regulator Modules (VRMs) Can lose more than 30% power in conversion losses –Cooling fans Software can reduce fan RPM when not needed SPUE ratios of are common today

Power Supply Unit Efficiency 80 PLUS initiative to promote PSU efficiency –80+% efficiency at 20%, 50%, 100% of rated load –Can be less than 80% efficient at idle power load First 80 PLUS PSU shipped in 2005

Server Useful Power Consumption DevicePower Usage Intel Xeon W GHz Quad Core130 W Intel Xeon E GHz Quad Core80W Intel Xeon E GHz Dual Core80W 7200RPM Hard Drive7W 10,000RPM Hard Drive14W 15,000RPM Hard Drive20W DDR2 DIMM1.65W Video Card20-120W The best method to determine power usage is to measure it

Server Utilization ~10-50% Figure 1. Average CPU utilization of more than 5,000 servers during a six-month period. Servers are rarely completely idle and seldom operate near their maximum utilization, instead operating most of the time at between 10 and 50 percent of their maximum It is surprisingly hard to achieve high levels of utilization of typical servers (and your home PC is even worse) “The Case for Energy-Proportional Computing,” Luiz André Barroso, Urs Hölzle, IEEE Computer, December 2007

Server Power Usage Range: % Figure 2. Server power usage and energy efficiency at varying utilization levels, from idle to peak performance. Even an energy-efficient server still consumes about half its full power when doing virtually no work. Energy efficiency = Utilization/Power “The Case for Energy-Proportional Computing,” Luiz André Barroso, Urs Hölzle, IEEE Computer, December 2007

Server Utilization vs. Latency Utilization 100% Latency

Improving Power Efficiency

Application consolidation –Reduce the number of applications by eliminating old applications in favor of new ones that can server the purpose of multiple old ones. –Allows elimination of old app servers. Server consolidation –Use single DB for multiple applications. –Move light services like NTP onto shared boxes. Use SAN storage –Local disks typically highly underused –Use SAN so servers share single storage pool

Improving Power Efficiency Virtualization –Host services on VMs instead of on physical servers –Host multiple virtual servers on single physical svr Only-as-needed Servers –Power down servers when not in use –Works best with cloud computing Granular capacity planning –Measure computing needs carefully –Buy minimal CPU, RAM, disk configuration based on your capacity measurements and forecasts

Containers Data Center in a shipping container. –4-10X normal data center density. –1000s of servers. –100s of kW of power. Advantages –Efficient cooling –High server density –Rapid deployment –Scalability Vendor offerings:

Microsoft Chicago Data Center

Google Container Patents Containers docked at central power spline Container air flow diagram, with a center cold aisle and hot air return behind servers Vertical stack of containers

Data Center Failure Events

Hardware Isn’t Reliable Enough If servers are 99% reliable, then a system with 10 servers is ≈ 90% reliable a system with 100 servers is ≈ 37% reliable

Fault-Tolerant Architecture Must use fault-tolerant software architecture –Hardware must detect faults –Hardware must notify software in timely fashion Fault-tolerant architecture reduces costs –Choose hardware reliability level that maximizes cost efficiency, not just reliability Fault-tolerant architecture can improve perf –Spreading processing and storage across many servers improves bandwidth and CPU capacity

Causes of Service Disruptions

Total Cost of Ownership (TCO) TCO = Data Center Depreciation + Data Center Operating Expenses (Opex) + Server Depreciation + Server Operating Expenses (Opex) Depreciation is the process of allocating cost of assets across period during which assets are used. Example: server cost = $10,000, $0 residual value annual depreciation over 4 years = $2500

Cost to Build Data Center Primary components (power, cooling, space) scale roughly linearly with space. 80% of total construction cost goes to power + cooling Typical depreciation periods of years

Operational Costs Operational costs include –Electricity –Salaries for personnel –Server maintenance contracts –Software licenses Larger data centers are cheaper –Smaller number of sysadmins per server –Fixed number of security guards For multi-MW data center, $0.02-$0.08/month

Case Study Tier 3 multi-MW data center –Dell 2950 III EnergySmart servers (300W, $6000) –Cost of electricity is 6.2/kW –Servers financed with 3-year 12% –Cost of DC construction is $15/W, 12-yr lifetime –DC opex is 4/month –PUE = 2.0 –Server lifetime is 3 years –Server maintenance is 5% of capex –Server avg power = 75% peak

Key Points Data center components –Physically secure space –Racks, the DC skeleton –Power, including UPS and PDU –Cooling –Networking Power efficiency (server cost = 4 years power on avg) –PUE = Data center power / IT equipment power –Most power in traditional DC goes to cooling, UPS –SPUE = Server PUE; inefficiencies from PSU, VRM, fans Cooling –Heat load estimation –Air flow control (hot/cold aisle architecture or containers) –Higher cold air temperatures (27C vs. 20C) –Free cooling (cooling towers) TCO = DC depr + DC opex + Svr depr + Svr opex

References 1.Luiz Andre Barroso and Urs Holzle, The Case for Energy- Proportional Computing, IEEE Computer, Vol 40, Issue 12, December Luiz Andre Barroso and Urs Holzle, The Datacenter as a Computer: An Introduction to the Design of Warehouse-Scale Machines, 1st edition, Morgan and Claypool Publishers 3.Xiaobo Fan, Wolf-Dietrich Weber, Luiz Andre Barroso, Power provisioning for a warehouse-sized computer, ISCA '07: Proceedings of the 34th annual international symposium on Computer architecture 4.Thomas A. Limoncelli, Christina J. Hogan, and Strata R. Chalup, The Practice of System and Network Administration, Second Edition, Addison-Wesley Professional, Evi Nemeth, Garth Snyder, Trent R. Hein, Ben Whaley, UNIX and Linux System Administration Handbook, 4 th edition, Prentice Hall, 2010.