Critical factors in intra-rack power distribution planning for high-density systems technology brief, 2 edition Abstract.............................. 2 Introduction............................2 Key factors of power distribution in high-density racks................3 Power level and phase........................3 Connector types..........................4 Power consumption .......................... 5 Space issues............................ 6 Segmented power distribution ......................
Abstract As server densities per rack increase, the power densities for those racks increase as well. This paper identifies critical factors that infrastructure designers and system administrators must consider to plan safe and efficient power distribution systems for high-density racks. Introduction Power distribution in the data center is changing with the continued increase in server density per rack.
Key factors of power distribution in high-density racks Power distribution units (PDUs) are highly recommended for high-density systems that place heavy loading demands on the facility alternating current (AC) power bus. PDUs allow IT infrastructure designers to: • Use segmented circuits to improve serviceability and enable sequential startup •...
Connector types Local and national electrical codes specify the types of connectors that should be used when interfacing with facility AC feeds. The location of the facility and the level, amount, and phase of the AC power available determine the type of connector to use. PDUs are designed to distribute power at a specific range and current.
Power consumption The type (low-line or high-line) and amount of power (in VA) required by the equipment in a rack largely determines the type of PDU(s) to use. HP provides online power calculators for making accurate power consumption estimates for most ProLiant servers. Each calculator (Figure 2) allows the IT infrastructure designer to predetermine the power requirements for a server chassis according to configuration parameters entered into the calculator.
Space issues The 1U and blade server form factors allow for high-density installations that can occupy 100 percent of the front U space in a rack. This leaves only rear U or side (“zero U”) space for mounting power distribution components. HP has designed components to address space issues that are becoming more acute in today’s high-density systems.
Segmented power distribution In high-density systems where a single rack can support hundreds of users at a time, the power infrastructure should be designed so that a single system failure will have minimal effect on overall operations. Segmenting servers into groups for power distribution reduces the chance for unscheduled downtime resulting from overload or maintenance conditions that might otherwise shut down everything else in the rack.
Redundant power distribution Redundant power systems require two power distribution circuits, one for each power bus. Redundant operation requires configuring servers with redundant power supplies, each capable of supporting the full load of a server, if necessary. For redundant operation, the PDU or PDUs for each bus should be configured to handle less than half of their rated capacity for normal operation so that they can handle the full load of the system if one bus fails.
Power circuit monitoring Enterprise data systems can be maintained efficiently with minimum manpower by employing components that continuously monitor current loading on power circuits. Monitored systems make it easier to balance power distribution circuits, to gauge expansion capabilities, and to avoid unscheduled downtime resulting from circuit overloading or equipment damage.
Sample power distribution solutions This section includes examples for implementing power distribution methods for various rack configurations. These configurations are examples only. Numerous configurations may be appropriate depending on factors mentioned earlier such as: • Server power consumption • Server configuration (number of processors, hard drives, expansion cards, etc.) •...
Table 2. Power distribution configurations for using one to four HP BladeSystem c7000 enclosures in a standard rack Total 1Ф 1Ф output No. of No. of output current Total output c7000 Input Recommended HP PDUs current available power enclosures Feed PDU with AC input plug type Reqd.
Rack configurations for distributing power to HP ProLiant DL servers This section describes power distribution configurations for a high-density server system based on HP ProLiant DL 360 G5 servers. The ProLiant DL 360 G5 is a 1U server that uses an auto-ranging power supply and supports power redundancy when used in the 1 + 1 power supply configuration option.