Sun System Handbook - ISO 3.4 June 2011 Internal/Partner Edition | |||
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Solution Type Technical Instruction Sure Solution 1010837.1 : Sun Fire[TM] 12K/15K/E20K/E25K, Sun Enterprise[TM] 10000 servers : Site Planning Considerations Using Redundant AC Power Sources
PreviouslyPublishedAs 214967 Description This document describes power planning considerations to minimize downtime for servers with N+1 Power Supply Redundancy or Dual Power Grid solutions. It discusses an example of a "fully loaded" Sun Fire[TM] 15K server, and explains the theories behind the answer to the question 'how many supplies are enough?'. The principles herein can be applied to all servers with N+1 Power Supply Redundancy, though it is specifically targeted at those with dual power grid AC infeed. NOTE: The E10000 only supports dual grid power with the optional Dual Grid Power installation. If the customer is aware of a PLANNED partial power outage, it is highly recommended to either power down affected systems -OR- bring them to the OBP prompt to faciliatate rapid return to operation once the planned partial power outage work has been completed. However, should the customer absolutely need to keep their system operational during a planned partial power outage, the information contained in this document will help to determine if such action is possible. Ultimately, the decision to keep the system powered up will rest with the customer after all factors are considered. Steps to Follow In the recommended configuration, the Sun Fire15K server should receive:
Ideally, each of the PDUs should be supplied from different Uninteruptable Power Supply (UPS) units, and different utility power grids. See the "Sun Fire 15K/12K Systems Site Planning Guide" (806-3510-14) chapter 3 for details. The Sun Fire 15K power system (using A141 power supplies) has been architected to be able to survive a complete power loss to one of its input power sources. (ie: Input 0 on all 6 power supplies, or one complete PDU). In the event of an external power loss, it is possible to have the system remain operational even with the loss of up to half of the external power cords or circuits (a whole PDU). A site may need to power off one of their power distribution units for maintenance and the question arises whether the system will stay running during the planned (or unplanned) power source outage. This may place a greater than expected load on the remaining functional PDU, if it has not been sized appropriately. Each PDU should be sized to be able to supply the required output to power the entire 15K frame. There is no direct way to determine what the current demand is on each of the external power cords. However, one can make some simple calculations to figure what an internal DC power supply demand approximately translates to in external AC circuit terms. Data obtained via showenvironment or similar interrogation commands will display some useful information regarding the power input to the system. Be aware the current values shown by the showenvironment command are the 48VDC ones. Several items must be kept in mind when observing these indications. 1. Power supply current demands are what is used at the DC voltage of the supply. For example - a 20.32A demand for PS0 is obtained at 48.80VDC. There may be a second amperage demand for PS0 if a second AC input cord is connected. If the second DC current indicated is also 20.32A, then total current draw for that power supply is 40.64A measured at 48.80VDC. 2. To determine what the facilities electrician will measure on the AC power cords connected to PS0, we must do some simple calculations. AC equivalent is found by dividing the DC wattage by the AC line voltage. For purposes of our example, we will assume a steady 208VAC. Therefore: Approximate AC current input on AC-0 is : 991.62W / 208VAC or 4.77A. 3. The above calculated AC input currents are approximate, as we have not compensated for factors such as power supply inefficiency. However, the calculated AC current input should be sufficient for planning purposes. 4. As an aside, if you note an obviously abnormal or disproportionate variation between the two current readings of any power supply, it would be wise to 5. Once we have determined what can be approximately expected on the external AC power cords, one can perform an assessment of the external power sources for sufficient capacity to handle the equipment under any operating condition. Let's look at a real world example to determine what the impact would be if one of the external AC power sources were to fail. Basically, we need to determine if the system will stay up. For purposes of this example, it is assumed the external power source is a well-regulated UPS providing steady 208 V AC power to the equipment circuits. For purposes of our example, the Sun Fire 15K (or similar) derives power from two power distribution units. Power from PDU-0 are supplied to the AC-0 input of each DC power supply and power from PDU-1 are supplied to the AC-1 input of each DC power supply. Situation is as follows: The customer needs to power down PDU-1 for some emergency maintenance. They want to know if the SF15K needs to be powered off during their maintenance or if they can remain operational. While it is highly recommended to power off systems during a planned partial power outage, this is not always possible due to operational demands on the system. If the customer absolutely needs to keep their system running (if possible), then details contained in this document will help them to make an informed decision to do so. F15K Frame#3 POWER VALUE UNIT STATUS --------- ----- ---- ------ PS0 Current0 20.32 A N/A Current1 20.32 A N/A 48VDC 48.80 V N/A Power 1983.23 W N/A Translates to external power cord readings of : 4.77A @ 208V AC (AC0 input) PS1 Current0 20.32 A N/A Current1 21.91 A N/A 48VDC 49.60 V N/A Power 2094.61 W N/A Translates to external power cord readings of : 4.85A @ 208V AC (AC0 input) PS2 Current0 21.51 A N/A Current1 20.32 A N/A 48VDC 49.40 V N/A Power 2066.40 W N/A Translates to external power cord readings of : 5.11A @ 208V AC (AC0 input) PS3 Current0 20.71 A N/A Current1 21.51 A N/A 48VDC 48.80 V N/A Power 2060.34 W N/A Translates to external power cord readings of : 4.86A @ 208V AC (AC0 input) PS4 Current0 21.91 A N/A Current1 20.32 A N/A 48VDC 49.40 V N/A Power 2086.16 W N/A Translates to external power cord readings of : 5.20A @ 208V AC (AC0 input) PS5 Current0 22.71 A N/A Current1 22.31 A N/A 48VDC 48.80 V N/A Power 2196.98 W N/A Translates to external power cord readings of : 5.33A @ 208V AC (AC0 input) Total Power 12487.72 W N/A Under fault conditions (ie: loss of one of two PDU feeding the frame) the current normally supplied from one PDU or the other will be shifted onto the surviving power source. As an example, assume the entire frame is powered from two power distribution units. Further assume the second PDU experiences a fault and drops power. All the AC-1 input current demands would shift to the surviving AC-0 power source. Examining this further : PS0 AC-0 current demand shifts from 4.77A@208V AC to 9.54A @208V AC PS1 AC-0 current demand shifts from 4.85A@208V AC to 10.07A @208V AC PS2 AC-0 current demand shifts from 5.11A@208V AC to 9.94A @208V AC PS3 AC-0 current demand shifts from 4.86A@208V AC to 9.91A @208V AC PS4 AC-0 current demand shifts from 5.20A@208V AC to 10.03A @208V AC PS5 AC-0 current demand shifts from 5.33A@208V AC to 10.56A @208V AC The surviving power source (PDU#1) has a sudden increase of 29.93A @208V AC Possible conclusions :
Product Sun Fire E25K Server Sun Fire E20K Server Sun Fire 15K Server Sun Fire 12K Server Sun Enterprise 10000 Server Sun Enterprise 10000 Dual Grid Power power, AC, DC, SF15K, HES, Current, Current0, Current1, dual, grid Previously Published As 81142 Change History Updated by the ESG Knowledge Content Team 4/2010 Attachments This solution has no attachment |
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