How it Works
Hewlett-Packard
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1U
User Manual
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Hewlett-Packard 1U User Manual

The HP BladeSystem p-Class 1U power enclosure: hot-plug, redundant power for a server blade enclosure
technology brief
Abstract.............................................................................................................................................. 3
Introduction......................................................................................................................................... 3
Components of the enclosure ................................................................................................................ 3
Hot-plug, redundant power supplies ................................................................................................... 3
Redundant AC power ....................................................................................................................... 4
Hot-plug power management module ................................................................................................. 5
Features of the enclosure ...................................................................................................................... 5
Bi-directional electronic e-fuse............................................................................................................ 5
Power zones.................................................................................................................................... 5
Dynamic power saver....................................................................................................................... 7
Serial port....................................................................................................................................... 8
Efficient cabling ............................................................................................................................. 10
Infrastructure configurations ................................................................................................................ 12
Using PDUs with the 1U power enclosure.......................................................................................... 13
Standard configurations.................................................................................................................. 15
Risks associated with extreme density ............................................................................................... 18
Supported configurations for the S348 Monitored PDU and S332 Monitored PDU................................. 18
Supported configurations for the 40 A PDU....................................................................................... 18
Using uninterruptible power supplies (UPS) with the 1U power enclosure .............................................. 20
Conclusion........................................................................................................................................ 21
For more information.......................................................................................................................... 22

Abstract

The HP BladeSystem p-Class1U power enclosure provides hot-plug, redundant power for a single enclosure of HP ProLiant BL p-Class server blades from standard single-phase AC inputs. A properly configured HP BladeSystem p-Class 1U power enclosure is an ideal power solution for small office and remote site blade deployments. This technology brief explains the 1U power enclosure operation and features as well as infrastructure configuration considerations. This paper is written with the assumption that readers are already familiar with the HP BladeSystem.

Introduction

The HP BladeSystem consists of modular components that enable IT administrators to readily modify and scale their infrastructures to meet changing IT demands. The ability to provide required power to servers and use it efficiently is a critical IT need. The HP BladeSystem includes two power subsystem options: a 3U power subsystem and a 1U power subsystem. This paper describes the 1U power subsystem only. Refer to subsystem.
The 1U power subsystem includes an HP BladeSystem p-Class 1U power enclosure configured with embedded power supplies and a power management module. Power supply and AC line cord redundancy is provided when powering one fully configured HP BladeSystem p-Class server blade enclosure. The power management module enables IT administrators to efficiently monitor and manage total enclosure power consumption.
www.hp.com/go/bladesystem for information about the 3U power
Choosing an optimal power solution requires the consideration of many factors, including the number of server enclosures needed, the type of server blades to be installed, and the type of available power. The HP BladeSystem p-Class 1U power enclosure is particularly well suited to the following IT environments:
• Small or mid-size businesses using server blades in their infrastructure
• Remote or branch offices with distributed server blade deployments
• IT environments with single-phase power requirements

Components of the enclosure

The HP BladeSystem 1U power enclosure supports high availability by providing hot-plug, redundant power supplies; redundant AC inputs; and a hot-plug power management module that operates independently of the server blades and interconnects.

Hot-plug, redundant power supplies

The 1U power enclosure houses up to six hot-plug power supplies, each unit rated at 2,000 W DC output power. The enclosed six power supply bays are divided into two sides with three bays on bus A and three bays on bus B (Figure 1 and Table 1).
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Figure 1. HP BladeSystem p-Class 1U power enclosure bays
Table 1. HP BladeSystem p-Class 1U power enclosure bay descriptions
Item Description Configuration
1 Power supply bay 1 Bus A
2 Power supply bay 2 Bus A
3 Power supply bay 3 Bus A
4 Power supply bay 4 Bus B
5 Power supply bay 5 Bus B
6 Power supply bay 6 Bus B
To implement a redundant configuration using power supplies in the 1U power enclosure, one or more of bays 1 through 3 and an equal number of bays 4 through 6 must be populated with a power supply.

Redundant AC power

For redundant AC power, bays 1 through 3 must be supplied with AC power from a different branch circuit than bays 4 through 6. Each bay must be supplied with single-phase AC power according to the specifications in the QuickSpecs, which are located at
http://h18004.www1.hp.com/products/quickspecs/12330_div/12330_div.html. The branch circuit
should have adequate capacity to handle the peak current demands of a fully populated 1U power enclosure when attached to a fully populated server blade enclosure.
If only one side of the power enclosure is populated with power supplies, the power subsystem is not redundant. If AC redundancy is not required, three power supplies located in any three bays can provide adequate power for a fully loaded server blade enclosure.
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Hot-plug power management module

The hot-plug power management module monitors the power subsystem components and regulates the power-up sequence of newly installed server blades and interconnect switches. The power management module is connected with cables to the server blade enclosure management module(s) to facilitate communication of management information, such as server blade and interconnect location, power supply budget, and health status.

Features of the enclosure

The HP BladeSystem p-Class 1U power enclosure provides for power subsystem management with the following features:
• Bi-directional electronic e-fuse provides prompt power up.
• Power zones provide communication and management capabilities between power enclosures and
supported server blade enclosures.
• Dynamic power saver achieves efficient power consumption.
• Serial port allows direct monitoring of the 1U power enclosure status.
• Efficient cabling reduces clutter in the area behind the 1U power enclosure.

Bi-directional electronic e-fuse

The 1U power enclosure has a bi-directional electronic e-fuse switch that connects the -48-V DC outputs on bus A to the -48-V DC outputs on bus B. Once a single power supply is installed in a bay on either side of the 1U power enclosure, that side of the power enclosure is immediately powered. Approximately 3 seconds later, the internal electronic e-fuse switch automatically closes, and the other side of the 1U power enclosure is powered as a result. In short, both sides of the 1U power enclosure are powered even if only one power supply is installed, and the 1U power enclosure can operate this way indefinitely. With only one power supply installed, the built-in power management software attempts to limit the number of blade servers allowed to power on. An administrator, however, can override the warning and manually power up the servers.
The only time the electronic switch in the HP BladeSystem p-Class 1U power enclosure opens is when there is a bus short in the power enclosure. If a bus short occurs in the power enclosure, the electronic e-fuse switch quickly separates bus A from bus B. The circuitry within the 1U power enclosure automatically and continuously monitors the faulted side. Once the fault is cleared, the electronic e­fuse switch resets and closes automatically restoring full power to both sides of the server blade enclosure. This is a rare situation.

Power zones

Power zones, when set properly, associate server blade enclosures with the power enclosure(s) that support them. This allows power information and alerts to be sent to the proper power management module or server blade management module when power conditions change. For example, if an administrator removes a power supply from the HP BladeSystem p-Class 1U power enclosure, notification is sent to the affected server blade enclosure in that power zone.
Power zones also define the startup sequence of the server blades when the entire rack needs to be restarted after a total power outage. The server blade enclosures communicate with the power enclosures in the rack to ensure that the server blades and enclosures are powered in sequence, rather than all at once, to prevent overloading the AC infrastructure. The sequence always runs from the top of the rack (power zone 6), top left-hand blade through the top and bottom row of the blades in that enclosure (if ProLiant BL30p or BL35p server blades are installed). The sequence then proceeds
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down to the next enclosure and continues until the bottom right blade in the bottom server blade enclosure is powered.
In a rack that contains many server blade enclosures, the sequencing process may cause a significant time delay before the last server blade is powered. However, this is preferable to the alternative—the possibility that the main breakers trip due to the excessive load on the AC infrastructure as all the server blade enclosures try to power simultaneously.
Firmware in mixed environments
When 1U power enclosures and 3U power enclosures are used in the same rack, the firmware must be upgraded to the latest version for correct power zone operation. As of firmware release 2.20, there are important changes in how power zones are managed. In firmware releases prior to 2.20, there were only two power zones (zone 1 and 2) that were set by a switch on the rear of 3U power enclosures. Firmware 2.20 provides the capability to have up to six power zones, based on the absolute maximum hardware that could fit into one rack. The power zone switch on the rear of the 3U power enclosure only has a setting for zone 1 and 2; new power zones start at 3 to avoid overlap with existing power zones. The primary difference in setting the new power zones is that they are not set by a switch on the power enclosure. The switch is still present on HP BladeSystem p-Class 3U power enclosures for legacy firmware, but firmware version 2.20 and above do not use the switch. The new power zones (3 and above) are set automatically by the firmware based on rack topology. Unlike the 3U power enclosure, the 1U power enclosure does not have a power zone switch because it was released with firmware 2.20.
Every power zone must include a power source (either the 1U power enclosure or the 3U power enclosure) and at least one server blade enclosure. In the pre-2.20 firmware environment, if a server blade enclosure were in zone 2 and the power enclosure supporting it were in zone 1, the server blades and switches in that sever blade enclosure would never power on automatically because the devices in the server blade enclosure must request power from a power source in their own zone in order to power on. If the power source is not in the same zone as the server blade enclosure, the request for power is not answered because power is not available in that zone.
To ensure that all power enclosures and server blade enclosures are configured in the proper zone, all enclosures in a rack should be upgraded to firmware 2.20. If one enclosure in an infrastructure is upgraded to firmware 2.20 and the other enclosures are not upgraded:
• The enclosure upgraded to 2.20 is put into power zone 3.
• The enclosures not upgraded are placed in power zone 1 or 2 (depending on the zone in which
the physical switch is set).
Once all the enclosures in a rack are upgraded to firmware 2.20, the switch setting on the rear of the enclosure no longer serves a functional purpose. After an upgrade to firmware 2.20, power zone 1 and 2 are no longer used since the power zones are set automatically by the firmware based on rack topology, not switch settings. HP does not support mixed firmware versions within the same infrastructure. All enclosures should have the same firmware version.
NOTE: For more information on upgrading your firmware, see Chapter 5 of
the “HP ProLiant BL System Best Practices Guide”:
http://h20000.www2.hp.com/bc/docs/support/UCR/SupportM anual/TPM_351359-001_rev1_us/TPM_351359­001_rev1_us.pdf.
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Dynamic power saver

The dynamic power saver feature in the HP BladeSystem p-Class 1U power enclosure provides for efficient use of power in the server blade enclosure. When this feature is enabled, total power consumption is monitored in real time. Power supplies are placed in a standby condition when the power demand from the server blade enclosure is low. As power demand increases, the standby power supplies activate as necessary to deliver the required power. This enables the power enclosure to operate at optimum efficiency.
Optimum efficiency can be achieved because of the power supply efficiency curve associated with any power supply. Power supply efficiency is simply a measure of power in versus power out, so at 50 percent efficiency 2,000 W in would equal 1,000 W out. The difference is wasted energy, which costs money.
Dynamic power saver recognizes that most power supplies operate less efficiently when lightly loaded and more efficiently when heavily loaded. A power supply installed in the 1U power enclosure running with a 10 percent load could have efficiency as low as 50 percent, but with a 50 percent load, efficiency increases to over 90 percent, providing a significant savings in power consumption. Dynamic power saver drives power supply efficiency by shifting the load so there is a heavier load on fewer power supplies as opposed to a lighter load on all the installed power supplies.
Redundancy with dynamic power saver
Redundant power is maintained in dynamic power saver mode. The 1U power enclosure ensures that at least two power supplies, one from bus A and one from bus B, are active. When dynamic power saver is enabled on a 1U power enclosure with six power supplies installed, a low load initiates the following sequence:
1. Initially all power supplies are powered as normal.
2. Power supplies installed in bay 3 and bay 6 are placed in standby.
3. Power supplies installed in bay 2 and bay 5 are placed in standby.
4. Power supplies installed in bay 1 and bay 4 are always powered at 50 percent load or less to
ensure redundancy.
The reverse sequence applies as the load increases. Power supplies that are on standby are activated in pairs and the load is shared so the maximum load on each feed is 50 percent. Equal distribution of the load ensures that redundancy is always maintained.
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