Monitoring and managing power consumption
Reg Readers tell it like it really is
You the Expert We set you a challenge to join our expert panel and answer questions from our readers on how to deal with your server challenges.
This week we've got the first of a series of instalments on this topic. We welcome the first contribution from our resident reader experts, Adam Salisbury and Trevor Pott.
You can read their advice, along with advice from Intel and Freeform Dynamics, below.
The question they tackle this week is:
Not all organisations perceive power consumption as a major challenge – until limits are reached. What can be done to pre-empt this situation, and what level of monitoring is both achievable and useful, given today’s server environments?
Until very recently power management and energy efficiency have both been areas that have neither required nor received any time, money or attention from the business. It has not been until now, when we are more carefully considering our impact on the environment and trying to squeeze the most out of every last penny, that our focus has turned to how much power our systems are using.
For some enterprise class organisations, entire teams exist who are devoted to managing power consumption, efficiency and cooling. But what exists for the small business, struggling to cut costs and improve efficiency when it matters most? Well a good start is using power calculators and capacity planners, now provided by most big server vendors. They are a potent and essential tool for establishing baseline power consumption figures, no matter what the size of your infrastructure and can be used to measure future savings.
For a smaller organisation, which has never previously considered addressing power and cooling issues, simple things - like cable management arms to improve exhaust airflow and using blanking panels to increase the flow of air through, rather than around, the servers - will reduce the cost of keeping racks cool. Calculating the heat output of servers and then organising them in the rack accordingly will also improve airflow efficiency.
If you’ve got an infrastructure big enough that your equipment spans aisles and not just racks, then it’s worth using the hot/cold aisle system. This is now almost a de facto standard in most heavyweight data centres.
Having the aforementioned baseline statistics for power consumption will allow you to more accurately justify the replacement of legacy servers and UPS equipment. This will leverage the vastly improved power efficient designs and technologies which have only recently been developed. In some instances, a new equivalent spec server or UPS can be up to 70% more efficient than its legacy counterpart.
Considering the potentially huge savings to be made from utilising this new green technology, now is the time to consider consolidation and/or virtualisation. A lot of companies are already embracing server virtualisation, but many are still re-deploying old servers as hypervisors rather than buying new equipment, which would reap yet more savings.
Investing in power monitoring systems for your infrastructure will almost certainly result in considerable savings being made. Solutions exist which can provide a wealth of highly granular information from individual servers to power distribution units - from racks to aisles of racks. All manner of information about both quantity and quality of power can be divined from systems like these and for some, all that is needed is to see this data before obvious inefficiencies are identified and remediated.
However, if your infrastructure doesn’t comprise a sprawling data centre spanning thousands of square feet, monitoring can only help so much. The high-end solutions that exist would be hard to justify for a medium sized business with an office-sized server room. Such a company would be limited in what they could do with the data.
Whatever route you choose, plan carefully, measure and if executed correctly, you can make a significant difference to your organisation's bottom line.
All good, common sense
Having gone through much of the process described, I can say that the comments are all good. OK, so we're definitely in the 'small' category with three racks and about 10kW of load, but the process is the same.
A year ago, we had an unmanaged and unmanagable setup - multiple small UPSs (all on their limit), no proper power system, no cable management, and what could best be described as a mess. We now have an expanded server room, with 3 new 47U racks, a single large modular UPS, and proper power distribution and network cable management. We get load data from the UPS, so we have graphs of that, plus graphs of air temperatures (we use just airflow for cooling).
ONe thing not mentioned, servers do indeed increase their power consumption according to environmental conditions. Overall, our power consumption varies by around 5% with inlet air temperature once it goes above about 20˚C. Since not all the servers actually have any power management (eg variable fan speeds), I suspect that some of the servers vary their loads by more than 5%.
The big challenge now is persuading the boss that we do need to upgrade the ventilation/cooling system - we only just managed last June, and at times we had servers raising over-temp alarms. I suspect that now it's cooled down, the boss will decide we don't need to do anything, and it will be too late when it turns hot again.