2/7/2011
CIT 668: System Architecture Data Centers I
Topics Data Center: A facility for housing a large amount of computer or communications equipment. 1. 2. 3. 4.
Racks Power PUE Cooling
Google DC in The Dalles, OR
Located near 3.1GW hydroelectric power station using Columbia River dams for power
1
2/7/2011
Google Data Center in The Dalles, OR
Inside a Data Center
Inside a Container Data Center
2
2/7/2011
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 http://uptimeinstitute.org/ for more details about tiers.
3
2/7/2011
Racks
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
4
2/7/2011
Rack Sizes
http://www.gtweb.net/rackframe.html
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.)
5
2/7/2011
Rack-Mount Servers
1U
4U
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.
6
2/7/2011
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.
Power
Data Center Power Distribution
http://www.42u.com/power/data-center-power.htm
7
2/7/2011
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
http://myuninterruptiblepowersupply.com/toplogy.htm
Online UPS • • • • •
AC -> DC -> AC conversion design True uninterrupted power without switching Extremely good power conditioning Longer battery life Higher price
http://myuninterruptiblepowersupply.com/toplogy.htm
8
2/7/2011
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 2005. – $3.5 billion for server cooling in 2005. – $20.5 billion for purchasing hardware in 2005.
9
2/7/2011
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 Efficiency (PUE)
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
10
2/7/2011
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
11
2/7/2011
Cooling a Data Center • Keep temperatures within 18-27 ◦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 (CRAC) • Large scale, highly reliable air conditioning units from companies like Liebert. • Cooling capacity measured in tons.
Waterworks for Data Center
12
2/7/2011
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
13
2/7/2011
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 18-20◦C. Use of free cooling: In moderate climates, cooling towers can eliminate majority of chiller runtime.
Server Power Usage Efficiency (SPUE)
Sources of Server Inefficiency 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 1.6-1.8 are common today
14
2/7/2011
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 Device
Power Usage
Intel Xeon W5590 3.33 GHz Quad Core
130 W
Intel Xeon E5430 2.66 GHz Quad Core
80W
Intel Xeon E5502 2.13 GHz Dual Core
80W
7200RPM Hard Drive
7W
10,000RPM Hard Drive
14W
15,000RPM Hard Drive
20W
DDR2 DIMM
1.65W
Video Card
20-120W
The best method to determine power usage is to measure it https://www.wattsupmeters.com/
Computation Efficiency
15
2/7/2011
Server Utilization Typically 10-50% “The Case for Energy-Proportional Computing,” Luiz André Barroso, Urs Hölzle, IEEE Computer, December 2007
It is surprisingly hard to achieve high levels of utilization of typical servers (and your home PC is even worse)
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
Server Power Usage Range: 50-100% “The Case for Energy-Proportional Computing,” Luiz André Barroso, Urs Hölzle, IEEE Computer, December 2007
Energy efficiency = Utilization/Power
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.
Latency
Server Utilization vs. Latency
Utilization
100%
16
2/7/2011
Improving Power Efficiency
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
17
2/7/2011
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)
References 1. 2. 3. 4.
5. 6.
Luiz Andre Barroso and Urs Holzle, The Case for Energy-Proportional Computing, IEEE Computer, Vol 40, Issue 12, December 2007. 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 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 Albert Greenberg, James R. Hamilton, Navendu Jain, Srikanth Kandula, Changhoon Kim, Parantap Lahiri, David A. Maltz, Parveen Patel, and Sudipta Sengupta. 2009. VL2: a scalable and flexible data center network. In Proceedings of the ACM SIGCOMM 2009 conference on Data communication (SIGCOMM '09). ACM, New York, NY, USA, 51-62. Thomas A. Limoncelli, Christina J. Hogan, and Strata R. Chalup, The Practice of System and Network Administration, Second Edition, AddisonWesley Professional, 2007. Evi Nemeth, Garth Snyder, Trent R. Hein, Ben Whaley, UNIX and Linux System Administration Handbook, 4th edition, Prentice Hall, 2010.
18
