The dramatic reductions in HDD cost per GB have resulted in many system/storage architects (and application/operating system programmers) treating primary storage as though it is free.

Some of the results are:

• Exponential increases in the size of operating systems and applications
• Mass deployment of low-end and midrange servers with multiple copies of data (and applications)
• Over-provisioning of storage to satisfy future needs projections (which also likely adopt the concept of free storage)
• Adoption of power-hungry DRAM cache appliances to mask HDD performance shortfalls
• Over-provisioning of HDDs to mask HDD performance shortfalls

These all result in inefficient use of storage that has many costs, not the least of which is the increasing cost of energy consumption.  Some of the energy data becoming available paints a sobering picture:

• Data centers account for 1.5% of ALL U.S. electrical consumption, and this is expected to double in a few years
• Power consumption per $1,000 of server spending has increased by a factor of 4 since 2000
• Power failure and availability is expected to halt data center operations at more than 90% of all companies over the next few years
• Fifty percent of current data centers will have insufficient power and cooling capacity this year

HDDs are clearly not the only contributor to the rapid acceleration of data center power consumption, but their inefficient use is likely one of the largest contributors.  Data that suggests more than one third of data center power consumption is storage related.

Trends and techniques such as consolidation, virtualization and thin provisioning should all contribute to improved efficiencies.  But while doing so, these approaches will put increased performance demands on the HDDs.  The result:  an increased need for higher performance (i.e., higher RPM……read that as ‘power consuming’) drives and even further over-provisioning for performance – and therefore once again increased energy consumption.

It’s time for new metrics to be considered in the data centers, which take into account energy usage to aid the system designers as they optimize their systems.  Several metrics are identified at the www.greendatastorage.com website; examples cited include activity per watt, such as transactions/Watt, IOPs/Watt, and bandwidth/Watt.

I believe that Enterprise Flash Drives (EFDs) will play a major role in reversing these trends. EFDs can provide over 1000x improvement in IOPs/Watt, and an order of magnitude or more improvement in bandwidth/Watt over the highest performing HDD’s.

Amyl Ahola

Ok, I want to get back to the issue I was discussing a couple of posts ago.

The question I’m exploring is what can be done about the growing gap between disk drive and enterprise network performance, as well as the escalating inefficiencies?   One only has to look at the root cause:  the mechanical nature of disk drives.  The solution is obvious; eliminate the mechanics. 

Easier said than done! 

The Holy Grail for primary storage has always been directly addressable low latency, non-volatile random access memory.  This remains a long way off, but it is time to begin the next evolutionary step.  Solid state technology (particularly Flash) cost and performance continues to improve geometrically, and new and even more competitive semiconductor storage technologies are around the corner.  Meanwhile, disk drive performance (seek, latency) is stagnating, with only limited foreseeable improvements and with cost per I/O leveling off or even beginning to increase with time. 

Last year Greg Schulz of the StorageIO Group predicted the increasing use of solid state technology in enterprise storage applications, saying (paraphrased) that 2008 will be the year of awareness and early adoption by vendors and early deployment by customers, while 2009 will be the broader adoption phase.   Supporting that projection, EMC has recently announced their commitment to Flash and is the first major enterprise storage company to do so (http://www.emc.com/about/news/press/us/2008/011408-1.htm).  Although it was a limited announcement with what I consider an ‘entry level’ SSD technology, it is the first step towards validation of Flash technology as an enterprise primary storage device.

Solid state storage has the potential to be transformational, relegating disk drives to applications that better match their strengths, low cost per GB and large block sequential applications (for the old timers amongst us, it should be noted this is similar to the role disk played years ago with respect to magnetic tape drives).

But Flash comes with its own set of problems…(Stay tuned)

Amyl Ahola

I was intrigued by a blog post by Chuck Hollis of EMC last week (“Chuck’s Blog”) offering an interesting perspective on the whole “green IT” issue:  http://chucksblog.typepad.com/chucks_blog/2008/03/green-it—-are.html. 

Chuck suggests that the IT industry may be missing the point on “green IT.”  Specifically, while it is important to pursue green IT goals from an energy efficiency perspective, the real goal should be “efficient IT,” which can, as a result, generate a number of green benefits, including improved power consumption and footprint reductions.  He further suggests that just because something is green, it doesn’t necessarily mean it is efficient.

I couldn’t agree more.  While I believe that green IT is a critical objective for virtually all enterprise IT environments, there are a number of IT efficiency issues that must be addressed now for their own sake.  Take the use of enterprise HDDs for example.  Many of today’s IT managers are using 3 to 4 times more HDDs than they need from a capacity perspective just to meet growing I/O performance requirements.   This “over provisioning” is at best a band-aid approach to improving I/O, and is probably one of the most inefficient uses of IT technology I’ve seen.

I’ll have more to say on this later, but for now I just wanted to note the importance of pursuing efficient IT for its own sake.  The benefits can be many, not the least of which is a greener IT environment.

Amyl Ahola

I have decided to depart from my planned comments because I can’t help but mention a recent storage announcement to help make the point of how far one can go to try and overcome HDD shortfalls.  The announcement references an array of small form factor drives (2 ½”) configured to achieve a very high ‘Actuator Density’ array — a noble objective.  According to the company’s white paper, the unit is sealed and contains 160 or more drives in a 3RU rack.  The drives apparently counter rotate and are offset from each other to overcome shock and vibration issues.

The white paper also talks about 160 drives plus 10 spares in this sealed unit with a three-year minimum life, resulting from the ‘Failure in Place’ ability to dynamically swap failed drives with self-contained spare drives.  Using their own MTBF data and typical failure statistics, this configuration would result in more than 10 failures in a three-year period in more than 50 percent of the installations.  Putting this in perspective:  more than 10 failures means replacing the entire sealed unit, and in the best case, requiring many hours recovering tens-of-TBs of data.  I would not want their warranty bill!

Given the actual failure rate of HDDs (especially consumer grade HDDs used in high duty cycle environments), and not the inflated specification numbers from HDD suppliers, I can’t imagine anyone who has experienced a catastrophic HDD failure event willing to take the risk on such a ‘sealed’ configuration that doesn’t allow hot swaps.  This seems to be marketing 101 at its best:  if you have a downside, feature it!

The white paper also propositions improvements in performance and power that, at least in this author’s opinion, when subjected to similar tests of objective analysis do not hold up.

My point is not to throw stones at this particular approach, but rather use it to illustrate the magnitude of the challenge in overcoming the inherent performance and reliability shortcomings of HDDs.  When the fundamental problem is the mechanical nature of the beast, the solution is not to keep adding more of the same. 

In one sense, this is not all that different from the political discussions of the day…the question boils down to, do you want more of the same or is it time for a new paradigm?

Amyl Ahola