Hewlett-Packard this week is delivering a new power capping technology that has been latent in its ProLiant rack and blade servers for the past several years. The technology - which is implemented in the system management software and service processors inside the servers - is called dynamic power capping, and it will help data center managers put a cap on server power consumption and thereby help them pack more servers into a given power budget.
Dynamic power capping is part of a family of technologies that HP calls Thermal Logic, which debuted with the company's second generation of blade servers in June 2006 and which was thereafter rolled out in the x64-based ProLiant rack servers and the Itanium-based Integrity servers last year.
With Thermal Logic, servers and their chassis are designed to have different zones that can be cooled independently, and the systems and their chassis are equipped with multiple sensors for analyzing power use and temperatures. Insight Control system management software then interfaces with these server features and the on-chip power stepping features of Intel and Advanced Micro Devices chips to scale up or down processing capacity.
The high-end c7000 blade chassis also has a 2,400-watt power supply that can be cut back to a 1,200-watt unit if there is not enough power draw (it's actually two 1,200-watt supplies working in tandem), so a single power supply can be run closer to its peak draw and deliver greater than 90 per cent efficiency. Power supplies are more energy efficient if they are running close to their peak. Having an over-powered supply in a machine that is not drawing many watts just creates unnecessary heat and fan noise.
According to Jim Ganthier, director of blade system marketing at HP, millions of servers that the company has shipped in the past two years can use the dynamic power capping feature, which is enabled through the Insight Control system management software and the Integrated Lights Out (ILO) service processors inside rack servers or blade chassis.
Insight Control can log power use in the machines over time, and then system administrators can put a cap on power usage for a machine based on historical data or based on the power density that they can cope with in their data center. Insight Control is not free, however. It costs $549 on a rack or tower server and $399 per blade server. The dynamic power capping feature is compatible with any supported operating system or hypervisor on the ProLiant and BladeSystem machinery.
Ganthier is pitching dynamic power capping as a means for HP to cram a lot more servers into a data center. Now, rather than have data centers look at the peak power draw on the server's backplate (which is never what a server actually uses in production), data center managers can take a look at their applications running on a machine and see what the real load is and then cap it. So instead of guessing 700 watts per server and then loading up the racks, you might see you only draw 300 watts in production most of the time, and so you can cap power draw at 300 watts per machine.
That lets you put more than twice as many machines in a rack than you might otherwise. Ganthier says the customer average is somewhere between 8,400 and 8,600 watts per rack for standard configurations of x64 servers these days, and HP also has the goal of allowing customers to take down that power draw per rack, not just get two times as many machines in the same space. In real customer settings, dynamic power capping has allowed customers to get a three-fold increase in server density with a minimal sacrifice in application performance - and allow them to know for sure that they will not exceed the power distribution and cooling capabilities of their data centers.
The other approach to power capping, of course, is to switch to non-standard parts in a server, such as super-efficient power supplies, low speed memory, low voltage processors, and so on, and then run the systems closer to their maximums. But this approach still does not cap absolute power draw in the systems, and it can't be said to be dynamic, either. With the power capping HP is rolling out, a generic server with high-speed parts can be told to run more slowly if the servers next to it are working harder doing a specific task and generating a lot of heat, or whole racks of machines in a hot zone in a data center can be told to cool it for a while.
Don't get the wrong idea. HP is not against using low-power parts in its machines. The latest BL460c G5 two-socket Xeon blade server from HP has had 44 watts removed from its thermal envelop through such engineering. HP has chosen the Xeon L5340 processor, low power FB-DIMM memory, and an integrated RAID 0/1 controller to cut back on power consumption, and over three years, the 25 per cent savings in power consumption compared to the prior BL460c blade server adds up to around $2,220 in electrical savings per enclosure. The barebones ProLiant BL460c G5 blade itself only costs $2,759.
The Environmental Protection Agency has been working on an Energy Star rating system for servers for the past two years, and Ganthier brags that when the EPS finally gets a spec out, HP's ProLiant machines will meet or exceed the spec. (Of course, HP has a pretty big hand in creating the spec, as do all server vendors, and there must be tremendous pressure to set the bar a little high so all IT vendors can all look like they are doing better than expected). Ganthier says the EPA Energy Star spec is due in the spring of next year, perhaps in April. ®