X-bit labs

Hard Disk Drive Power Consumption Measurements: X-bit’s Methodology Indepth

Category: Storage

by Oleg Artamonov

[ 12/06/2007 | 04:02 PM ]

Our today’s article discusses in detail X-bit proprietary methodology for HDD power consumption measurements. We will talk about power consumption measuring techniques, there cons and pros, and explain how this type of measurements will be done for all our HDD reviews from now on.

Table of contents:

• Introduction
  
• Testing Methodology
  
• Multimeter vs. Oscilloscope
  

Introduction

Hard disk drive storage capacity and performance are traditionally considered to be the main parameters of a hard disk drive that are worth paying special attention to. Of course, both these parameters, especially the second one, have a lot of different aspects that we can look at, but in most cases, the hardware editors’ attention is given solely to these two things.

Such hard disk drive characteristic as power consumption has long remained unattended. You may think that it is pretty insignificant: what can a dozen watts really do for the system, if a contemporary graphics card or CPU consume more by a factor of 10x? However, this assumption is erroneous.

First of all, power consumption discussions have become very acute among hardware manufacturers lately. For example, the new Energy Star 4.0 standard indicates that the hard disk drive should consume 7W at the most in idle mode, which is 14% of the total PC power consumption (taking into account advanced CPU power saving modes, 14% of the total office PC power needs in idle mode may be not that much in the end). There are a lot of factors affecting it: environmental concerns, the lack of energy systems power capacity in industrially developed countries, intention to lower power bills… of course, these savings are tiny within a single computer environment, but if we remember that a single office building these days may contains hundreds and hundreds of machines, the end numbers may be pretty significant.

Secondly, and it is more important for us, hard disk drive power consumption equals its heat dissipation, heat dissipation determines its temperature provided all other conditions are equal, and HDD temperature is directly representative of the mean time before failure. For example, if you check out a pretty well-known study made by Google Called "Failure Trends in Large Disk Drive Population" (PDF file, 242KB), you will see that the probability of the new hard disk drives failure does not depend that much on their temperature any more, while the ones that are about three years old have much higher chances of failing if their temperature exceeds 40ºC.

So, by selecting a more economical hard drive, we can ensure that it will heat up less and hence will work more reliably over a longer period of time. It is especially important for compact MicroATX cases, many of which cannot accommodate additional fans for HDD cooling. However, even in large cases you may face an overheating problem if the system features 3-5 hard drives.

Thirdly, hard disk drives are currently used not only in desktop PCs, but also in notebooks: it will take another considerably while before they switch to SSD (Solid State Drive). And although notebook hard drives are by far not the most power hungry components, we shouldn’t disregard them completely: they do require certain amount of battery life as well.

Fourthly, many consumers and computer users buy 2.5” hard disk drives as portable storage devices inside USB chassis. A lot of chassis like that have no additional power supply, while a single USB connector can provide maximum 500mA current. So, some hard drives requiring a lot of power may face serious stability problems or may not be recognized by the system at all.

It is especially interesting to measure the HDDs power consumption because the HDD manufacturers have been working hard on making their solutions as energy efficient as possible lately. For instance, Hitachi has recently announced the launch of their energy efficient Deskstar P7K500 hard drives for desktop computers that use the same power-saving technologies as notebook drives.

Today we are going to point out a few problems you may come across when trying to measure HDD power consumption and offer solutions for them. From now on we are going to use the methodology described in this article on a regular basis in our HDD reviews and roundups.