adam's notes

Networking Power Management

  • all network appliances require stable power supply to operate
    • can fail from
      • voltage spikes or surges
      • under-voltage event
        • voltage drops briefly
      • power failure
        • complete power loss for few seconds or more

Power management means deploying systems to ensure equipment is protected and network operations can continue uninterrupted or recovered quickly.

Dual Power Supplies

  • enterprise-class server or appliance enclosure is likely to feature two or more power supply units (PSUs) for redundancy
  • hot plug PSU can be replaced without powering down the system

Power Load and Voltage

  • circuits supplying grid power must meet the load capacity of all the installed equipment and room for growth
  • AC circuits to a server room will be higher capacity than domestic or office circuits
    • 30 or 60 amps vs 13 amps
    • may run higher voltage (240 VAC vs 120 VAC)
  • power supply for each appliance has a wattage rating
    • calculate as
  • Max load:

Example

Max load for rack:

Power Distribution Units

  • each circuit might run through a power distribution unit (PDU)
    • An advanced strip socket that provides filtered output voltage
  • Has circuitry to “clean” the power signal
  • protects against spikes, surges, and under-voltage events
  • can integrate with a uninterruptible power supply (UPS)
  • available as strip sockets
    • can take higher load than a common 13 amp rated strip
  • managed PDU supports remote power monitoring functions:
    • reporting load and status
    • switching power to a socket on/off
    • switching sockets on in a particular sequence

Battery Backups and Uninterruptible Power Supplies

  • battery backup can sustain power for few minutes or hours
  • can be provisioned at the component level for storage device or array cache
    • battery protects any read or write operations cached at the time of power loss
  • uninterruptible power supply (UPS) provides a temporary power source in the event of a power failure
    • desktop-rated model can run a few minutes
    • enterprise system rated can run a few hours
    • comprises a bank of batteries and their charging circuit plus an inverter to generate AC voltage from the direct current (DC) voltage supplied by the batteries
    • different form factors and power outputs available

Generators

Backup power generator is a standby power supply that provides power to the whole building, often for several days.

  • fuel source:
    • diesel
    • propane
    • or natural gas
  • drawback of diesel and propane:
    • safe storage
    • diesel has shelf life of 18 mo – 2 yr
  • drawback of natural gas:
    • is having a reliable gas supply in the event of a natural disaster
  • Datacenters are investing in renewable power sources
    • solar
    • wind
    • geothermal
    • hydrogen fuel cells
    • hydro
  • ability to use renewable power is a strong factor in determining the best site for new datacenters
  • alternatives:
    • Large-scale battery solutions
    • emerging technologies that use all the battery resources of a datacenter as a microgrid for power storage

Info

A UPS is always required to protect against any interruption to computer services, as a backup generator cannot be brought online fast enough to respond to a power failure.

  • Generator power is typically introduced via transfer switches that can operate either manually or automatically
  • The UPS must be sized appropriately to handle power requirements during the transfer process

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