Achieving Rapid Scale in Enterprise and Cloud Data Centers with SAS. Seagate Mark E. Wojtasiak

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1 Achieving Rapid Scale in Enterprise and Cloud Data Centers with SAS Seagate Mark E. Wojtasiak Xyratex Michael K. Connolly Michael A. Hoard Linda Tillis, P.E.

2 Notices The information in this document is subject to change without notice. While every effort has been made to ensure that all information in this document is accurate, the document is provided as-is and Xyratex accepts no liability for any errors that may arise. Reliance on this document and its content is at the sole risk of the viewer or reader Xyratex (the trading name of Xyratex Technology Limited). Registered Office: Langstone Road, Havant, Hampshire, PO9 1SA, England. Registered number No part of this document may be transmitted or copied in any form, or by any means, for any purpose, without the written permission of Xyratex. Xyratex is a trademark of Xyratex Technology Limited. All other brand and product names are registered marks of their respective proprietors. For more information please contact marketing@xyratex.com or visit Issue 1.1 August 2013

3 Executive Summary Since the advent of the hard disk drive, the amount of data created has grown year over year. Never has data growth been faster than in the era we live today, as shown in figure 1. Cloud services, for example, are a highgrowth sector for storage requirements in the next five years, with Gartner stating the total public cloud services market size in 2011 was $91.4 billion, and is expected to grow to $206.6 billion in , and Infrastructure as a Service (IaaS) revenue, specifically storage, will account for a large part of that growth. There are a number of trends driving data growth in addition to Cloud Social Media, BYOD, Big Data Analytics but we need not go into why data is growing, or even how we are managing the growth. The more important question to answer is: What are we doing to prepare our server and storage infrastructure to not only meet the demands around exploding storage capacity needs and still deliver unprecedented levels of performance, scalability, and reliability? Introduction 1 Figure 1: Data Growth Projection from 2011 to 2020 Source for graphic: Seagate Market Research & Competitive Intelligence. storageeffect.media.seagate. com/2012/09/storage-effect/ chart-the-location-of-data-ischanging/ With the explosion of data over the past decade, storage technology was forced to evolve. In the early years of enterprise storage, parallel SCSI reigned supreme as the interface of choice for server based storage. As networks evolved, the concept of accessing data from shared pools of storage resources commonly referred to as Storage Area Networks (SAN) gave rise and growth of the Fiber Channel interface. At this point, parallel SCSI dominated server and direct attach storage (DAS) architectures, while Fiber Channel dominated the SAN. It was at this time that both the ATA desktop interface, and SCSI enterprise DAS interface were becoming serialized. The introduction of the Serial AT Attachment (SATA) and Serial Attach SCSI (SAS) interfaces led to a boom in desktop and enterprise storage transformations. SATA was quickly adopted as the standard interface for client compute delivering faster throughput, thinner more manageable cabling, and greater signal integrity. At the same time, SAS quickly began battling Fiber Channel in the enterprise DAS and SAN spaces, but Network Attach Storage (NAS) and the iscsi protocol was emerging as a low cost challenger with wider connectivity: Network Attach Storage (NAS) and the iscsi protocol. Positioned at the lower end, these Ethernet based storage offerings tended to draw upon inexpensive desktop class SATA drives. How Did We Get Here? With the growth of NAS and iscsi storage, the large installed base of Ethernet cabling within businesses of all sizes were being leveraged for storage. Quickly, lower cost NAS solutions enabled seamless connectivity with department level and workgroup clients, displacing the back-end data center realm previously held exclusively by enterprise level SAN, and the desktop class SATA drive was introduced into the enterprise. Because desktop class SATA hard drives were less expensive, as were SATA controllers, plus the benefit that SATA could function on a SAS backplane, both NAS and DAS solutions began using desktop SATA drives for low cost high capacity storage, but this approach was not without issues. Desktop class SATA drives were not designed for the 24x7 duty cycles demanded in an enterprise environment. Customers experienced degradation of performance, and poor reliability, as shown in later sections of this paper. A primary culprit: rotational vibration. Too many hard drives running non-stop in a system caused the system to vibrate leading to a significant degradation of Input/Output Operations Per Second (IOPS) and reliability. 1 Gartner.com (2012). Gartner Says Worldwide Cloud Services Market to Surpass $109 Billion in Retrieved 1 November 2012 from Gartner.com:

4 2 The big problem, desktop class hard drives continue to proliferate into what are marketed as enterprise class storage solutions. Is this a good thing? Will users have the expertise to constantly read between the lines and accurately gauge slogans from reality and consequences at the end of the day? When data grows at the pace it is growing now and forecasted to grow, companies tend to look for any and all opportunities to drive cost out of their storage solutions. It has become habit for many to simply choose the highest capacity storage solution they can find at the lowest possible cost. In many cases, the solution ends up utilizing a desktop class hard drive product not designed for enterprise workloads and duty cycles. The use of lower end commodity technologies derived from department level and workgroup clients as well as Considering the use of desktop drives in your environment? Consider that Map/Reduce via Hadoop, often viewed as an example where design theory celebrates commodity piece parts and can encompass low bandwidth 1Gbps Ethernet between loosely coupled, bare-rack storage-processing nodes populated with inexpensive drives. The reality, though, is that a serious deployment scheme such as Map/Reduce leverages a variety of optimization methods, as well as high performance storage, networks, compute nodes and sophisticated data management tools. 2 The premise of using inexpensive storage-processing nodes with inexpensive desktop drives should be weighed against numerous factors including, but not limited to, specific application characteristics, optimization alternatives synergistic with data work flow structure, as well as available team skills and resources. Indeed, the use of cheap desktop hard drives is only one alternative and not necessarily the best first choice. the blending, merging and displacement of former data center and enterprise techniques underscore the need for broad industry education regarding the facts about storage technologies. The issue is not with individual technologies but, as mentioned, the blending, merging and displacement. How do organizations and users assess the mix of technologies being purchased or otherwise utilized within their infrastructures? Optimal Placement and Use of Drive Technologies Specifically, this paper presents insights to help manage the optimal placement and use of drive technologies, as shown in figure 2, to help avoid the consequences of misplaced perceptions and expectations. Performance Enterprise-class drives must maintain high performance levels in multi-drive configurations where physical vibrations transmitted through a cabinet occur. This phenomenon is known as Rotational Vibration (RV). RV itself is a twisting and torque action experienced by a hard drive. RV is measured in radians as the angular rate of change in seconds in other words, it s how much angular acceleration movement the drive can handle. The main sources of RV energy are: 1 Hard drive seek movements 2 Additional drives inside the cabinet accessing data (e.g. multi-spindle environments) 3 External forces acting on the cabinet. If RV is not taken into account in the design of the drive, the force of RV can push the head off track causing missed revolutions and delays in data transfers. Tests on drives not capable of handling RV have shown significant reductions (over 50%) in performance. Fortunately, enterprise drives have used numerous technologies for over a decade to negate the effects of RV. To optimize these densely packed, multi-drive environments, Seagate uses RV sensors as well as linear vibration sensors on its enterprise class drives. These sensors enable the drive to compensate for any vibration that occurs 2 Map/Reduce on Lustre, Hadoop Performance in HPC Environments, Nathan Rutman,

5 from the drive itself or outside of the drive (e.g. cooling fans, poorer-quality chassis, etc.) and still continue to read and write data. It s also a good idea, by design, to reduce the amount of vibration that a drive may generate on its own. Seagate s high capacity enterprise drives are built using a Top-Cover- Attach spindle motor that increases rigidity within any drive that uses a 4-disk configuration. Further enhancements of the design are made by optimizing the seek profiles of the drives in firmware to minimize any emitted torque. Designing the drive to reduce RV from the start is only the beginning. When drives are placed together within a single enclosure, even small RV transmissions from each drive can result in affects across all of the drives. Xyratex utilizes thermal modulation and drive isolation techniques from various vibration sources (e.g. fans and other moving components) or by choosing components that minimize vibration, such as weighted fans, to create ideal individual drive test environments. This allows Seagate and other drive vendors to recognize increased drive performance, density, and operational flexibility as well as allowing Xyratex to design and produce modular enclosures and high performance application platform solutions with very dense storage capacities. Xyratex works closely with Seagate in qualifying their drives with performance testing within its processes and enclosures Figure 2: Drive Technologies Spanning from Desktop to Enterprise 3 How does rotational vibration affect hard-drive operation? In a hard disk drive, the read/write heads follow concentric tracks on the disk platters. Head position must remain within an allowable tolerance window for read and write operations to occur. The allowable write window is smaller than the allowable read window making write operations more sensitive to vibration than read operations. If the writer position exceeds the allowable position-window then the write operation is temporarily stopped. A write-position-window violation is called a write-fault. The write operation resumes once tracking accuracy returns within the allowable window and the target write location (logical block address, LBA) passes under the writer. The target LBA passes under the writer once-per-disk-revolution. When a write-fault occurs the write operation usually resumes one disk revolution later. Under extreme vibration the write operation may be delayed for several disk revolutions. Delayed read/write operations are the root of all vibration induced I/O degradation. The bottom line: customers with multi-drive applications will benefit Are all cloud services alike? The infrastructure of cloud services, usually viewed as a monolithic sea of bare-rack servers with exposed motherboards and inexpensive hard drives, actually varies from service provider to service provider. The reality, behind the scenes, in next-generation public cloud services is the inclusion of compute and storage solution stacks tailored to high performance database and custom applications, where the hardware and software are highly optimized to yield record-breaking response times, transaction loading, and sustained throughput. To achieve reliable and sustained performance at cloud scale, these premium analytics services would struggle to compete using inexpensive desktop hard drives due to the better sustained match of high-performance enterprise drives to the needs. Taking the user applications that use the infrastructure into consideration is critical. Failing to match applications to the right technology can cause major loss of data, outages, and, ultimately, national news. The allure and novelty of the cloud cannot interfere with establishing a solid match between solution and practice. Users need to know exactly what they are buying and exercise full knowledge at all times. An overly simplistic or general view is just plain dangerous.

6 4 greatly from actually achieving the specified performance levels made available by integrating enterprise-class drives across multiple storage tiers. Scalability and Data Integrity In order to meet growing data demands, businesses look for solutions that provide the greatest level of scalability. Being able to expand network storage capacity quickly and cost effectively without disrupting service level agreements is critical in today s world of Terabytes, Petabytes, even Exabytes of data. With the move to storage networks also comes the need for more advanced error checking. Getting data from a motherboard to a directly attached drive is one thing. Getting that same information through multiple switching points, whether within a server rack or across the country, is something else. Every point where there is an address change introduces an opportunity for error. Desktop drives use basic error checking, but there is nothing in the drive that says, I need to make sure that the information I m receiving is the exact same information that was originally sent to me. If a bit gets flipped in-transit, a desktop drive will record the error and not know any better. Enterprise drives will use advanced methods, similar to those used with ECC server memory, along with metadata embedded in the information stream to identify and remedy miscompared errors. Reliability As mentioned within this paper, in most cases, poor drive reliability is usually a result of deploying the wrong type of storage device within an enterprise class system, or for a specific enterprise class workload. Hard disk drives, being mechanical devices, are designed with specific features and components for specific workloads. An enterprise class drive is equipped with additional features and functionality that allow it to reliably read and write data in a more stressed 24x7 data center environment. Conclusion It is obvious that decisions by organizations and service providers that utilize desktop drives in dense rack environments are made based on low cost. However, consider the fact that desktop drives, while being lower cost, have less stringent design parameters to keep the product and industry costs low. Whereas enterprise drives foster reliability and high availability as the main driver in the design criteria with advanced technology included (that is not used in desktop drives) such as improved RV tolerance. Key Takeaways 1 Storage requirements are continuing to grow exponentially with no slow down in sight. 2 Desktop drives are not designed for data center and multi-spindle environments with sustained performance, scalability and reliability requirements. 3 Not all data centers and infrastructure are equal and the related performance ability of any environment must match the requirements necessary for critical applications. 4 Organizations expecting to purchase reliable sustained storage performance at scale are advised to seek out and demand the better sustained match of high-performance enterprise drives to the needs. While we touched on some of the actual technology variances between desktop and enterprise drives throughout this paper, an entire paper will be necessary to expound in detail the capabilities and differences between various nearline drives. Seagate and Xyratex will release a follow up paper on this exact subject in the very near future so stay tuned.

7 1 United Kingdom Headquarters Langstone Road Havant Hampshire PO9 1SA United Kingdom T: +44(0) F: +44(0) Principal US Office Lakeview Blvd. Fremont CA USA T: F: Xyratex (The trading name of Xyratex Technology Limited). Registered in England & Wales. Company no: Registered Office: Langstone Road, Havant, Hampshire PO9 1SA, England. The information given in this brochure is for marketing purposes and is not intended to be a specification nor to provide the basis for a warranty. The products and their details are subject to change. For a detailed specification or if you need to meet a specific requirement please contact Xyratex. No part of this document may be transmitted, copied, or used in any form, or by any means, for any purpose (other than for the purpose for which it was disclosed), without the written permission of Xyratex Technology Limited.