A guide to server efficiency

Alan Stevens ZDNet.co.uk

Published: 05 Jun 2007

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Power management
Again it’s down to the processor vendors to provide this, an example being AMD's Power Now! Optimized Power Management (OPM) technology available on the latest multi-core Opteron chips. OPM can fine-tune clock speed and voltage requirements automatically depending on CPU workloads; AMD claims efficiency gains of up to 75 per cent during idle periods using this technology.

Intel, naturally, has something similar called Demand Based Switching (DBS), which is an extension of the SpeedStep technology long available on Intel's mobile processors, for which similar claims are made.

Motherboard vendors are also helping here, incorporating additional remote monitoring and management functionality into their designs. And if you look in detail at the latest operating system products you’ll find an increasing emphasis on the ability to make efficient use of hardware resources. Turning off unwanted processes for example or, on the latest Windows Server 2008 and most Linux distributions, not even installing them in the first place.

Elsewhere, server and network management tools are being adapted to better monitor and control power and cooling, while vendors such as Dell are now offering customers capacity planning tools to better estimate power, cooling, airflow and other requirements.

Form factor
Another complication is the form factor, with servers seemingly getting smaller by the month. As such, rack-optimised products have now all but replaced old-style tower servers — at least as far as the enterprise datacentre is concerned. But these in their turn are now being rapidly phased out, and although rack-optimised servers are still being deployed, for maximum processor density and the ultimate in potential efficiency, blade servers are the way forward.

Traditional tower-format servers (above left) have largely been replaced by rack-mounted units (above right), which in turn are now being superseded by potentially more power-efficient blade servers (above centre).

Essentially single-board computers, blade servers are designed to slot into a special rack-mount chassis to provide maximum processing power in the minimum space. Power and cooling are handled through the enclosure rather than on the blades themselves, minimising the components involved and making blade solutions much more efficient compared to their ordinary rack-optimised equivalents. Even so, it’s possible to get much the same specification on a blade as in a rack-optimised server.

That’s partly down to the fact that a blade doesn’t need its own power supply, cooling fan or bulky air flow ducting. But equally, the introduction of multi-core processors means more processing power in less space. You can also now get high-capacity memory modules and much smaller disk drives — HP, for example, is standardising on 2.5in. SAS (Serial Attached SCSI) drives across its entire ProLiant server range, with other server vendors taking a similar approach.

Of course you can encounter similar problems with blades to those outlined previously for multi-core processors. Blade servers let you do more with less, but growth in demand can mean moving from cabinets packed with rack-optimised servers to enclosures of similar size chock-full of blades. Moreover, first-generation blades empahsised performance, with little consideration given to power management or cooling. That's now changing, with the likes of HP, Dell and IBM increasingly keen to push the power management features of their latest blade products.

Thermostatically controlled fans able to react to changing conditions are now very much the order of the day in the latest products. Indeed, some vendors have even gone as far as patenting their fan technology, as with HP and the fans in its latest c-Class ProLiant blade enclosures. You’ll also find additional circuitry dedicated to monitoring and managing power and cooling, not only on the blades themselves but also through additional controllers to manage complete blade enclosures and racks plus custom software for secure remote management.

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