Considerations for Using Solid-State Storage as an Intelligent Cache to Accelerate Applications

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1 A UBM TECH WHITE PAPER MAY 2013 Considerations for Using Solid-State Storage as an Intelligent Cache to Accelerate Applications Four critical questions to ask before adopting flash technology in the data center Brought to you by

2 2 Four Critical Questions to Consider Before Adopting PCIe SSD in the Data Center EXECUTIVE SUMMARY Solid-state disk (SSD) technologies are top of mind in most discussions of enterprise storage infrastructure today. Considerable attention has been focused on the idea of leveraging cost-effective, PCIeattached solid-state memory to speed transaction processing, augment the speed and throughput of traditional hard disk drives, and reduce overall IT infrastructure power demand. All in all, the technical case for PCIe-attached SSD has been established, but there are still IT planners who have postponed the adoption of flash memory-based storage in their environments, typically owing to concerns over acquisition cost or early adoption risk. This white paper gives IT planners the latest available information on PCIe-attached SSD to bolster the business value case for flash technology investment today. When evaluating any technology for adoption into the enterprise IT infrastructure, an IT planner typically considers four questions carefully: 1. What is the issue that needs to be remedied? How does it affect business processes, IT operations and customer engagement? 2. Are the technology costs, including acquisition, implementation and operations, offset by the benefits? Benefits can be measured in terms of improved business process efficiency, faster customer transactions, less downtime and even lower energy costs, to name a few. 3. What are the management and administration challenges? Technology that cannot be managed or administered readily from the requirements definition phase through the maintenance phase of its useful life will have a higher cost of ownership over time. Planners need to evaluate the sustainability of the technology and the capability of managing it with available staff skills and knowledge. 4. Is the technology fit to the purpose for which it is being deployed? If there are alternatives for meeting requirements, why is this technology better than the alternatives? Today, these questions are being extended to core technologies, including data storage infrastructure, that were once acquired almost as an afterthought. What Storage Infrastructure Issues Do You Want to Address? Determining the suitability of PCIe-attached SSD to address issues in storage infrastructure first requires a clear understanding of what the issues are. In general, the issues may be divided into three broad categories. The first issue is the accelerating demand for storage capacity and its associated cost. Disk storage now consumes a significant percentage of IT capital expenditures, accounting for 33 to 70 cents of every dollar spent on IT hardware, depending on the analyst you consult. This reflects the growth in storage capacity demand, which is on track to climb from around 21 exabytes in 2011 to as high as 140 and 212 exabytes by 2014, according to leading industry analysts. This trend concerns not only the technical planners, who want greater engineering efficiency (more output with less input), but also the nontechnical decision makers who control the budget in the front office. Storage is beginning to look like a nail in search of a cost-cutting hammer. A second issue is the increasing demand for energy required to power ever-larger storage infrastructure. From an operational cost standpoint, disk storage is becoming the leading consumer of electrical power in today s data centers more than servers or communications equipment. Supplying power to arrays is only

3 3 search of a cost-cutting hammer. Storage is beginning to look like a nail in part of the load: The significant amount of heat generated by disks, power supplies and other storage infrastructure components also must be dissipated. Given the rising cost of electricity and the increasing challenges in distributing utility power to where it is needed, it is not surprising to see energy moving from the domain of the facilities budget to that of the IT operations budget, where it is becoming a more important factor in IT infrastructure planning and design. Third, applications and general server workloads have begun to tax the throughput of traditional disk storage to a greater degree than ever before. Planners are seeking ways and means to boost input/output (I/O) operations that will not require fielding significantly more disk capacity or growing associated energy demand beyond reasonable limits. To IT planners, these are issues that require some remedy. And PCIe-attached SSD is increasingly viewed as part of the solution that is being sought. The Costs and Benefits of Flash Storage With the central issues identified, the next step in developing a strategy is for planners to identify the costs and benefits of technologies identified as potential remedies. Over the past few years, analysts and pundits have given considerable attention to the costs and benefits of substituting flash memory-based storage for traditional hard disk drives. Such simplistic reviews tended to focus on the relative benefits of each storage medium in terms of capacity and cost per gigabyte, and throughput and input/output per second (IOPS). Disk drives tended to win capacity-oriented analyses, while flash-based solid state disks (SSD) win the IOPS comparison. Making the technology case for flash SSD required that vendors address the two key issues of nonlinear performance and memory wear. Critics described flash storage performance as nonlinear once data had been written to an SSD, subsequent write operations required an extra step erasing cells of old data so that new data could be written. This two-stage write operation, also known as write amplification, reduced the throughput of the SSD by 50 percent, critics observed, from what it delivered when first deployed. Memory wear referred to the limits in the number of times that data could be written to memory cells in flash memory before the cell could no longer be written to. These are important issues to consider when analyzing potential benefits and drawbacks of PCIe-attached SSD. The good news is that LSI has introduced a technology called Redundant Array of Independent Silicon Elements (RAISE ) that delivers significantly lower failure rates of individual cells and significantly greater SSD total life. Complementing this controller improvement is LSI DuraWrite technology, which uses intelligent lossless data compression to handle flash memory cells more elegantly, improving both performance and durability. The bottom line is that IT planners who have been putting off the decision to introduce flash technology into their storage infrastructure until issues such as memory wear and nonlinear performance have been adequately addressed can now be sure that these concerns have been met. Numerous white papers and customer case studies are available today that confirm the benefits of LSI technologies for improving the resiliency and endurance of PCIe-attached SSD products. Improved durability is only one cost mitigator of flash storage. To perceive the real cost-containment enabled by flash SSD, one needs to consider storage against the backdrop of energy consumption. Recently, a disk array vendor achieved 450,000 IOPS in an industry-standard performance test an accomplishment that required approximately 1,920 magnetic disk drives operating in parallel. Other vendors have achieved comparable throughput using more disk drives in their arrays, with each drive configured for short stroking a technique to increase drive throughput by limiting the number of tracks that the read/write head traverses. At 5 to 7 watts per drive, the record-setting array consumes a significant amount of utility power about 13.5 kilowatts. Leveraging flash SSD, power-related operational expense can be reduced significantly. In a hybrid solution, flash memory, such as LSI Nytro MegaRAID, is used to provide a read cache for disk, enabling the use of fewer magnetic disk drives to obtain the same performance as hundreds or thousands of parallelized disk drives. In operation, when data is written to disk and subsequently receives a large quantity of concurrent access requests, it is copied into a flash memory and served to requestors at rates in excess of

4 20,000 IOPS per SSD. Over time, when this hot data cools (e.g., when read requests fall in number and frequency), new requests can be pointed to the location of the data on disk, and the copy on the flash can be erased. As suggested in Figure 1, using a PCIe RAID storage adapter to provide intelligent caching of hot data optimizes the performance and throughput of the disk storage infrastructure as a whole, while reducing the number of disk drives required and the energy they consume. That represents a significant cost-benefit advantage in terms of hardware acquisition, maintenance expense, improved user productivity and transaction processing. Intelligent Caching Optimizes Performance of the Storage Infrastructure Huge aggregated power demand. Fewer disks optimized with Flash SSD s-1000s of parallel disks to achieve IOPS. Significantly improved IOPS, but significantly lower power demand. Figure 1: Using a PCIe RAID storage adapter to provide intelligent caching of hot data optimizes the performance and throughput of the storage infrastructure while reducing the number of drives and the energy they consume. Any Management and Administration Challenges? In addition to concerns about durability and reliability, IT managers have been delaying the adoption of flash storage because of concerns about management and administration requirements. Until recently, it was difficult and expensive to determine which applications would benefit from flash memory. How much flash componentry would be needed to achieve a desired throughput level for a given workload was another straightforward question for which there were few easy answers. LSI saw these challenges and created Nytro Predictor software to facilitate the development of an intelligent and effective flash storage implementation plan. Nytro Predictor is a valuable tool for determining whether flash caching and I/O acceleration will improve application performance. Application performance is only partly determined by storage performance and I/O throughput. To determine whether an application is storage-bound, planners need to look at server CPU utilization and the queue lengths of hard disk drive storage. The first metric shows whether the processor is waiting for data, while the second shows whether application I/O instructions are stacking up and waiting for execution at the disk. Leading server operating systems, including Microsoft and Linux, provide tools for collecting these metrics, but what would be really useful is an analytical tool that can take this data and provide guidance for using PCIe-attached SSD to optimize performance and I/O. LSI Nytro Predictor software is often used before a Nytro solution is deployed to monitor and report how much hot data a customer s application is generating and how it could be effectively addressed by flash caching. The product provides an easy-to-understand dashboard display of the I/O issues it has detected and what the expected result will be of deploying a cache of a given size to address the problem.

5 Figure 2: LSI Nytro Predictor provides an easy-to-understand dashboard of the I/O issues it has detected and the expected result of deploying a cache of a given size to address the problem. 5 With tools such as the Nytro Predictor, native facilities such as Microsoft xperf or Linux blktrace can be harnessed to determine whether applications will benefit from flash caching. Moreover, Nytro Predictor quickly identifies the capacity of the flash device required to do the job. Once deployed, LSI Nytro application acceleration products work in conjunction with LSI intelligent caching software to monitor file systems for hot spots. Frequently accessed data is immediately cached and served out of the LSI flash card until it cools and new hot data replaces it. From the standpoint of operational management requirements, LSI Nytro family flash memory IT planners who have put off the decision to introduce flash into their storage infrastructure until issues of memory wear and nonlinear performance have been addressed can now be sure that these concerns have been met. products contain no moving parts to maintain and no user configuration setups to modify. They do include a management infrastructure for extensive monitoring of operational status, error rates and failures. The administrative and management overhead of the technology is virtually nonexistent. Fit for Purpose? With a clear-headed understanding of the issues that need to be addressed, the costs and benefits of the selected technology, and its long-tail requirements for management and administration, IT planners can usually address the fourth question quickly and easily. PCIe-attached SSD has a compelling technical and business value case, and LSI Nytro flash-based storage is already delivering practical and sustainable solutions for application performance acceleration and storage infrastructure cost-containment. The ultimate benefit of an effective PCIeattached SSD strategy is the improved productivity it enables. Users will experience faster access to data and more nimble application response. That can add up to better overall business performance. This paper provides a high-level summary of the technical and business value case for flash storage technology generally and for LSI Nytro flash-based storage in particular. For IT planners who are still sitting on the fence regarding flash, the time to wait is over. The cost benefits, manageability and fitness-to-purpose of PCIe-attached SSD storage technology has arrived. ABOUT LSI LSI Corporation (NYSE: LSI) designs semiconductors and software that accelerate storage and networking in data centers, mobile networks and client computing. Our technology is the intelligence critical for enhanced application performance and is applied in solutions created in collaboration with our partners. More information is available at UBM Tech, a division of UBM LLC. All Rights Reserved.