Storage Peer Incite: Notes from Wikibon’s December 04, 2007 Research Meeting
This week Wikibon presents Spinning climate in the data center. This edition focuses on the increasing amount of power, and therefore cooling, being consumed by the various disk arrays in the data center and throughout the corporation, and what storage managers can do to control that growth. Our conclusions are that moving to 2.5" disks can have an impact but that migrating to tiered storage and using lower performance disk drives with better power use profiles for Tier 2 and Tier 3 may be even more effective.
Of course disk drives are only a part of the picture, and any effort by storage administrators to improve their corporation's energy use profile should be part of a larger plan covering the entire corporation. Equally important for the IT Organization (ITO), which is one of the largest energy users in most companies, is to document how it actually has a net positive impact on the corporate carbon footprint and how existing technologies can be leveraged to greatly improve the overall organizational posture. For instance, by changing corporate policies and leveraging IT capabilities, many organizations can create a large body of "flexi-workers" who work from home two or three days a week. By scheduling their in-office days across the week, the organization can have those flexi-workers share office space, cutting the total floor space of corporate offices and therefore heating and cooling, as well as decreasing traffic congestion, pollution from the vehicles of commuting workers, and traffic accidents involving employees. Companies doing this have also consistently found that employee morale, productivity and retention have increased, saving the organization money in several areas. BT has used such methods to cut its carbon signature corporate-wide by 60%, while reducing operational costs and maintaining steady corporate growth over the last decade. Bert Latamore
The issue of energy consumption continues to grip the imagination of consumers, business executives and policy makers. IT storage professionals also must become aware of the relationship between faster, denser devices with higher performance levels and overall energy consumption and green implications. However, many IT professionals are uncertain about their ability to manage storage energy consumption, in part because of a built-in expectation at the application level of greater storage performance, higher capacities, and lower costs. They also see disk drives as component items chosen by array vendors and entering the data center as parts of larger systems, and therefore not under the storage administrator's direct control.
While these concerns are justified, IT professionals can make important choices in disk drive selection as part of their effort to reduce data center energy consumption. The two primary variables determining disk drive energy consumption are RPM and diameter. Energy consumption varies directly with disk RPM at approximately a 3:1 ratio (that is, energy consumption increases three times as fast as RPM increases) and directly with disk diameter at a 5:1 ratio. This means that reducing the size of disk drives from the present 3.5” to 2.5” can have a significant impact on drive energy consumption.
However, areal densities are not increasing fast enough to completely make up for the decrease in physical area of the smaller disks. Therefore, more platters must be added to provide the same storage capacity, which reduces the net power savings. At the same time, the smaller disks take up half the total space of the larger, older disks. The result is that in some situations the power, and heat, density of the resulting arrays can be 300% higher than those they replace.
We expect the transition from 3.5” to 2.5” disk drives will take place in high performance storage arrays in the next 12-18 months. This will probably lead to reintroduction of liquid cooling in some of these arrays and the data centers where they are housed. These heat and energy issues will probably allow 3.5” drives to sustain their market viability in tier 2 and 3 applications.
Meanwhile, users seeking to reduce the energy cost and carbon footprint of their storage systems might first want to investigate turning off spares. This, however, can cause conflicts with applications that presume striping, which spreads storage across all available drives. ITOs also should aggressively pursue tiered storage strategies that will allow them to deploy lower-performance drives with lower energy profiles for the fast-growing tier 2 and 3/bulk applications.
Energy concerns are likely to catalyze a call for the appointment of an individual with the authority and responsibility of bringing coherence to the ITO's overall strategy for minimizing the heat and energy challenges in the data centers, including new approaches to designing and deploying data center capacities.
Action Item: ITOs should not presume that storage is a given in their overall green strategies. While a green storage strategy is not synonymous with an overall green strategy, IT storage professionals can and should start taking steps to facilitate that overall green strategy in the business. These steps will require that storage administrators be very clear about the relationship between disk drives and energy when discussing green issues both with the rest of IT and the larger business. They should consider speedy adoption of technologies like tiered storage that will increase their degrees of freedom in choices on IT and energy.
IT loses the trust of the business when power becomes a problem. IT power consumption is a CFO/CEO issue in many businesses. Data centers have run out of power without warning. Consolidation initiatives with millions in savings have been put on hold or rolled back. When IT lost the trust of business with out-of-control CAPEX spending at the turn of the millennium, IT was moved back to the CFO. IT needs to be seen as proactive rather than reactive to power and green issues or risk reporting to a facilities manager renamed as the “Energy Czar” or “KVA King”.
All IT executives including storage managers must be able to answer three questions:
- What is the power and power density requirements now and over the next five to ten years?
- What initiatives are in place to ameliorate IT power consumption and carbon production?
- What contribution do the IT applications supported make to corporate power consumption and carbon production?
Action Item: Make IT cool and green by:
- Taking charge of IT power costs; take facilities costs as an IT line item and reflect it back in business chargebacks.
- Project storage and other IT power consumption and carbon production over the next five to ten years.
- Champion aggressive tiered storage initiatives.
- Include a section in every business case for storage or other IT power consuming equipment on the power and carbon savings from the applications supported.
- Work with storage and other IT vendors with corporate wide carbon neutral initiatives.
All complex challenges ultimately require an institutional response. Changing the energy profile of an IT organization won't be any different. While suppliers will trumpet relatively quick fix products and services, real solutions to energy and heat challenges will require a focused change effort that should be run by a core team, led by a strong leader, and reporting as close as possible to the CIO.
This group should have a simple but coherent portfolio of responsibilities: transferring corporate green objectives into achievable green IT goals; collaborating directly with corporate and business groups running facilities; scanning the market for real power and energy solutions; drafting and negotiating green change plans with decision makers both internal and external to IT; formulating an "architecture overlay" for power that could evolve into a schematic for considering application, infrastructure, sourcing, and cost-relief decisions; introducing and advocating green data center concepts in projects for modernizing or adding data center capacity; and packaging a coherent story regarding an IT organization's response to corporate energy and power mandates. This effort should be attached to real budget, real talent, and real authorities.
Action Item: Green IT won't just happen: strong, focused leadership will be required to drive meaningful change in concert with business objectives. Appointing a "VP of Green" now will allow IT organizations to help lead corporate green change, and not just be moved by it.
In short, we are running out of things to tweak as discussed in (see Green_Storage_--_Do_Disk_Drives_Matter?_Yes,_but_....).
For enterprise-class drives, there are simply fewer degrees of freedom because we are reaching the limits of air cooling and recording surface area. Historically, developers could vary:
- Areal Density,
- Platter Diameter,
- Rotational Speed (RPM),
- Number of platters,
- Seek Times/ Actuator Speed.
In the past, all of these contributed to a steady progression of smaller and smaller drives still providing equal or better capacity and performance. However, this progression is near its end because:
- Areal densities are becoming harder to increase.
- Smaller platters such as those in 2.5" drives have too little surface area to meet market demand for high capacities.
- Drive vendors can add platters to achieve the required capacities, but the 1U server vendors can’t cool them. And this is the bulk of the market.
- Rotational speeds over 15,000 RPM generate too much heat.
- Faster seek times need too much heat, or the mechanical parts are too big.
Nonetheless, the industry is shifting to 2.5" drives for tier 1 storage, although to meet capacity demands, suppliers will require more spindles than with 3.5" drives. Moreover, 2.5" is likely to be the last in the progression of form factor reductions, as semiconductor technologies encroach on lower capacity ranges. Perhaps the disk array vendors will convince the drive vendors to produce 2.5" devices with more platters and therefore more capacity, but this will take two to three years to play out, and the drives will carry a premium cost.
Note that the market for slower 3.5" SATA drives will remain robust for non-tier 1 applications, perhaps extending the life of this form factor.
Action Item: For those who are desperate – out of power or cooling - the best strategy is to deploy lower RPM drives and look to water cooling if possible. For those who are not desperate, the best strategy is to wait for the vendors to commit to their green storage strategies while addressing the organizational issues discussed in Can_IT_be_cool_again?.
The enterprise storage business is exhibiting increased diversity driven by the explosion in data and rising energy costs. This is most evident and obvious with the advent of higher capacity SATA devices in the enterprise to support archiving, compliance and growing tier 2 and tier 3 applications. But other innovations are coming to the forefront of storage design as well, including the resurgence of solid state disks, technologies that spin down devices that are not in use (e.g. MAID) and virtual tape configurations that actually include tape. Virtualization technologies at the file and block level, including thin provisioning are becoming more popular and clustered storage (e.g. Google File System) is gaining attention of buyers and sellers alike.
It is becoming clear that while the design of storage systems increasingly includes these hybrid technologies, the focus of innovation remains in software to exploit hardware to both reduce costs and lower energy consumption. Tiered storage remains one of the most compelling and promising approaches to solving these problems and all major enterprise storage suppliers must be able to articulate a compelling tiered storage strategy, ideally without having to wait for a complete ILM vision to materialize. Suppliers will take a variety of approaches to tiered storage (with varying degrees of classification and automated data movement), and should start out with simple steps that can include:
- In-box tiering; an approach EMC is aggressively driving bringing high capacity devices into existing architectures like DMX;
- Virtualization engines that allocate diverse assets to different tiers (e.g. EMC Invista, Hitachi USPVM and IBM SVC);
- Simplified automated tiering within an architecture (e.g. Compellent);
- Over time, more advanced automation that includes anticipatory staging of data and device spin down where possible.
The challenge for vendors is finding the right mix. For example, while approaches like wide striping are popular in accounts that do thin provisioning, the very fact that data is so spread out makes spindown more difficult, because all devices contain critical data. Clustered storage brings similar challenges where spreading data everywhere and being able to rapidly recover from failure may be counterpoised to reducing energy costs using techniques like intelligent spin down.
One wild card in this diversity equation remains cooling and specifically liquid cooling. As Fred Moore has said: "Air moves heat; chilled water re-moves heat." This is potentially a niche area in storage that will grow in importance and might even provide leverage into the data center for new entrants.
Action Item: Storage vendors are faced with a wide variety of technology innovations that in combination can solve real problems for users. As packaging advancements increasingly accommodate lots of different components, suppliers should focus efforts not on the devices themselves but the software to automate data placement and optimize costs, including energy expenses. Cooling, especially liquid cooling remains a variable and is a potential threat and opportunity for existing players and upstarts alike.
An effective green initiative starts with the recognition that attitudes must change in order to impact behavior. Specifically, while there are many considerations, the following three points are noteworthy for IT:
- Understand that energy is not someone else’s problem. Communicate this throughout the entire organization, get out ahead of the momentum and lead the charge.
- Integrate facilities and IT or at least set up processes to formally share best practices across these two typically disparate organizations.
- Get rid of notions that suggest liquid cooling is somehow archaic and outdated. Air remains an inferior coolant, and U.S. companies are behind international counterparts at adopting liquid cooling.
Taking a holistic approach to the problem is good business. For example, IBM, based on customer studies, estimates that for every $1 spent on reducing energy consumption, $6-$8 is returned to the organization in terms of labor savings, reduced software costs, improved utilization, reduced floor space consumption and overall more efficient IT. Fundamental to this approach is putting in place effective monitoring and measurement capabilities that can identify the problem and perhaps more importantly, assign costs and ultimately affect ongoing improvements.
Action Item: IT organizations have an opportunity to participate actively in energy reduction strategies and must act urgently to quantify the problem, change perceptions and benchmark progress. Embracing this reality will allow organizations to preserve service levels, streamline infrastructure and demonstrate ongoing bottom line financial impact.