Green and SASy = Energy and Economic, Effective Storage

By Greg Schulz, Founder,

To say that "green" is a popular trend is an understatement. Green messaging in general and the information technology (IT) industry in particular tend to center around carbon footprint and emissions reduction or cost savings. Green is also being seen or talked about as being dead or falling off in importance and relevance.

While green hype and "green washing" may be falling out of favor or appearing on an endangered species list, addressing core IT data center issues that affect how resources are used to deliver information services is gaining attention. In an energy-efficient, environmentally and economically friendly manner, the industry is boosting efficiency and productivity and the trend is here to stay.

Business Issues and Drivers
Mention green and energy-efficient storage and most people assume either low-cost, high-capacity slow SATA disk drives used for consolidating under-utilized storage, magnetic tape, or MAID and Intelligent Power Management (IPM).¹ IPM-enabled MAID 2.0² (Massive Array of Idle Disks) storage addresses tactical and energy-avoidance scenarios. However, there is a growing awareness that strategically, energy efficiency and green storage, particularly for active and on-line storage, addresses energy efficiency. They process more work, store more information in a denser, more energy-efficient manner and are complimentary to energy avoidance for inactive and offline data and storage needs.

Energy costs are rising, floor space is at a premium in some organizations and soon will be exhausted in others. Cooling and electrical power distribution capabilities are strained or at their limits. Existing and emerging regulations for Environmental Health & Safety (EHS) as well as for emissions and energy efficiency are appearing. All of these factors continue to stress an aging infrastructure, which effects business growth and economic sustainability, resiliency and availability as well as operations cost complexity. Meanwhile, businesses of all sizes have a growing dependence on availability and timely access to IT resources and data.

After cooling the facilities for all IT equipment and providing server energy usage (Figure 1), external data storage has the next largest impact on power, cooling, floor space and environmental (PCFE) considerations in most environments. In addition to being one of the largest users of electrical power and floor space, with corresponding environmental impact, the amount of data being stored and the size of its data footprint continues to expand.

More data can be stored (Figure 1) in the same or smaller physical footprint than in the past, thus requiring less power and cooling. However data growth rates, necessary to sustain business growth in addition to enhanced IT service delivery and new applications are placing continued demands on available PCFE resources.

Figure 1: Do More in Same or Small Footprint without Degrading Quality of Service

Energy Avoidance: Tactical Avoidance and Conservation Address Immediate Issues
There is a lot of focus on energy avoidance (Figure 2), as it is relatively easy to understand and also easy to implement. Turning off the lights and turning off devices when they are not in use enables low-power, energy-savings or Energy Star® modes which are means to saving or reducing energy consumption, emissions, and energy bills. Ideal candidates for powering down when not in use or inactive include desktop workstations, PCs, laptops, and associated video monitors and printers. Turning lights off or implementing motion detectors to turn lights off automatically, along with powering off or enabling energy-saving modes on general-purpose and consumer products has a significant benefit.

Given the shared nature of their use along with various intersystem dependencies, not all data center resources can be powered off completely. Some forms of storage devices can be powered off when they are not in use, such as offline storage devices or mediums for backups and archiving. Technologies such as magnetic tape or removable hard disk drives that do not need power when they are not in use can be used for storing inactive and dormant data.

Figure 2 shows four basic approaches (in addition to doing nothing) to energy efficiency. One approach is to avoid energy usage, similar to following a rationing model, but this approach will affect the amount of work that can be accomplished. Another approach is to do more work using the same amount of energy, boosting energy efficiency, or the complement—do the same work using less energy. The energy efficiency gap is the difference between the amount of work accomplished or information stored in a given footprint and the energy consumed. In other words, the bigger the energy efficiency gap, the better. As seen in the fourth scenario, doing more work or storing more information in a smaller footprint uses less energy.

Figure 2: Shift from Energy Avoidance to Energy Efficiency and Productivity

Energy Efficiency: Shift to Efficiency and Productivity for Business Sustainability
Avoiding energy use is part of an overall approach to boosting efficiency and addressing PCFE challenges, particularly for servers, storage, and networks that do not need to be used or accessible at all times. However, for applications and data that need to be available and accessible, boosting energy efficiency is an important and strategic topic. Simply put, when work needs to be done or information needs to be stored, retrieved or moved, it should be done in the most energy-efficient manner aligned to a given level of service.

Instead of measuring how much power is avoided by turning equipment off, for active applications such as data, servers, storage and networks, the metric becomes how much data can be stored in a given footprint. The data still has to be accessible in a given time frame to meet service-level objectives. For example, by maximizing energy efficiency, more work can be done with highly energy-efficient servers and storage that process more transactions, IOPS (input/output operations per second), or bandwidth per watt of energy. Another measurement is how much work, how many transactions, how many files or email requests, how many users or video streams can be processed in a given amount of time. It has to be as fast as possible with the least amount of energy being used to power and cool equipment.

Tiered Storage: Balancing Business Needs with PCFE and PACE Requirements
Tiered storage is an umbrella term and is often referred to by the type of HDD, by the price band, or by the architecture. Tiered storage embraces tiered media, including different types and classes of HDDs, which vary in performance, availability, capacity and energy usage. Other storage media such as SSDs, magnetic tape, optical and holographic storage devices are also used in tiered storage.

Tiered storage—various types of storage media configured for different levels of performance, availability, capacity and energy (PACE)—is a means to align the appropriate type of IT resources to a given set of application service requirements. Price bands are a way of categorizing disk storage systems based on price to align with various markets and usage scenarios. For example, consumer, small office/home office and low-end-small-to-medium-size business (SMB) start in a price band of under $6,000; mid-to-high-end SMB in middle price bands go into the low $100,000 range; and small-to-large enterprise systems range from a few hundred thousand dollars to millions of dollars.

Figure 3: Tiered Storage - Balancing PACE and PCFE to Business Needs

Figure 3 shows examples of how tiered storage can be aligned. The lower left portion illustrates the use of high-performance HDDs and applicable RAID configurations to meet Tier 1 service needs measured on a cost-per-transaction basis. The upper right portion shows the other extreme, the most capacity with lowest performance and optimum energy efficiency of offline tape and optical storage. The IT balancing act is to align a given tier of storage to specific application or data needs using PACE resources in an optimal way.

Another dimension of tiered storage is tiered access, meaning the type of storage I/O interface and protocol or access method used for storing and retrieving data. Examples are high-speed 8Gb Fibre Channel (8GFC) and 10Gb Fibre Channel over Ethernet (10FCoE) versus older and slower 4GFC or low-cost 1Gb Ethernet (1GbE). Moreover, high-performance 10GbE-based iSCSI for shared storage access, Serial Attached SCSI (SAS) and Serial ATA (SATA) for direct attached storage (DAS), or shared storage between a pair of clustered servers are gaining in popularity as solutions today.

Compare different tiered storage media based on what applications and types of data access they will be supporting while considering cost and physical footprint. Also consider the PACE efficiency for the usage case, such as active or idle data. As an example, a current-generation 146GB, 15,500 (15.5K)-RPM, 4Gb Fibre Channel or SAS 3.5-inch HDD consumes the same, if not less, power than a 750GB, 7,200 (7.2K)-RPM SATA or SAS 3.5-inch HDD.

For active online data, the 15.5K-RPM HDD delivers more performance³ per unit of energy than the larger-capacity SATA HDD. However, for capacity-intensive applications that do not need high performance, the SATA drive has better density per unit of energy in the same physical footprint as the faster 146GB HDD. Which drive to use depends on the application. Increasingly, a mix of high-speed FC or SAS drives is configured in a denser storage system with some number of lower performing, high-capacity or aka "fat" HDDs for a tiered storage solution in a box.

SAS: Helping to Keep Disk Drives Relevant For Data Storage
As a technology, magnetic HDDs are over 50 years old. They have evolved significantly over that time, increasing usable capacity, performance, and availability while reducing physical footprint, power consumption, and cost. The mainstays of data center storage solutions today are based on 3.5-inch high-performance enterprise and high-capacity desktop HDDs along with emerging small-form-factor 2.5-inch high-performance enterprise HDDs. With a growing focus on "green" storage and addressing power, cooling and floor-space issues, a popular trend is to consolidate data from multiple smaller HDDs onto a larger capacity HDD. This boosts storage capacity versus energy usage for a given density ratio. For idle or inactive data, consolidating storage is an approach to addressing PCFE issues; however, for active data, using a high-performance drive to do more work using fewer HDDs is also a form of energy efficiency.

For those who think that the magnetic HDD is now dead, in actuality, just as disk is helping to keep magnetic tape around, SSD (both DRAM and FLASH) will help take some performance pressure off HDDs. They can then be leveraged in more efficient and economical ways, similar to what disk is to tape today. While magnetic HDDs continue to decline in price per capacity, FLASH price per gigabyte is declining at a faster rate, which makes storage using SSDs a very complementary technology pairing to balance performance, availability, capacity and energy across different application tiers.

Addressing green and PCFE issues is a process; there is no one single solution or magic formula. Rather, a combination of technologies, techniques and best practices to address various issues and requirements is needed. Keep performance, availability, capacity and energy (PACE) in balance to meet application service requirements and avoid introducing performance bottlenecks in the quest to reduce or maximize existing IT resources including power and cooling. Green washing and green hype may fade away but PCFE and related issues will not, so addressing them is essential to IT, business growth and economic sustainability in an environmentally friendly manner.

Bottom line, use common sense combined with best practices, including applicable RAID level to balance PACE to a given service level and cost requirement. Leverage new technologies with time-tested processes and procedures to address pertinent economic, energy and environmental efficient topics. Learn more in my new book, "The Green and Virtual Data Center" (CRC) at

¹ StorageIO Industry Trends & Perspective Report: "Intelligent Power Management (IPM) and MAID 2.0"
² StorageIO Industry Trends & Perspective Report: "Many Faces of MAID"
³ StorageIO Industry Trends and Perspective Report "Data Center I/O Performance Issues and Impacts"