Measuring the True Performance of Today s SATA and SAS RAID Controllers

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Damon Preston
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1 S T O R A G E S O L U T I O N S W H I T E PA P E R Measuring the True Performance of Today s SATA and SAS RAID Controllers Contents 1. Introduction...1 The Impact of Disk Choice on Performance Storage Server Applications and Usage Models OLTP Adaptec Controllers are Optimised for Your Real-World Workloads Unified Serial Controller-Enhanced Performance Introduction One of the difficulties of choosing a RAID controller is that you can t really know how it will perform in your environment until you already have it installed. All too often, RAID vendors quote irrelevant measurements to demonstrate the maximum performance of their RAID controller, and don t demonstrate how your RAID controller will hold up under a real-world application environment. Performance measurements in the IT world can be defined in many different ways. But ultimately, what matters is matching up the right performance metric to your storage server s workload environment. Consider an automobile analogy. What is the best measurement of performance? Acceleration? Top end speed? Storage? Fuel economy? The answers to these questions will determine the kind of vehicle best suited for a particular job. A dragster is a poor choice for a Grand Prix, while a Formula 1 race car is a poor choice for hauling timber (and you probably don t want a little sports car to pull your ski boat to the lake.) The same can be said for data storage. In order to select the right storage subsystem for the job, the performance requirements for the work to be done needs to be understood. In this paper, we will consider the performance requirements and real-world performance comparisons for the following workloads: s (OLTP) s s 4. Performance Analysis SATA Drives PCI-X & 16 SATA Drives PCIe & 16 SAS Drives PCIe...4 SATA or SAS? Yes!...4 Increased Value with Adaptec. It s More Than Just Performance Summary System Setup...5 The Impact of Disk Choice on Performance Due to improved Internet bandwidth and availability, along with the latest technological advances, storage requirements are exploding at an annual growth rate of 40-60%. 1 Markets such as video, imaging and audio, archiving, databases, with its ever-growing attachments, and document services are driving the need for high-availability, high-performing storage subsystems. Government regulations are requiring digital content to be stored for longer periods of time. At the same time, legal and liability concerns are increasing the need to maintain digital records for protection against lawsuits. With increasing storage capacity needs and shrinking IT budgets, more and more industries are turning to Serial ATA (SATA) disks as either primary or secondary storage. SATA disks are cheaper per gigabyte (GB) and generally have larger capacities than enterprise SCSI or Serial Attached SCSI (SAS) drives. Although manufacturers are continually improving their performance and reliability, SATA disks continue to have limitations, including slower access times, less tolerance for environmental vibrations and higher probability of failure. Still, SATA disk drives are being used in a variety of applications where SCSI disks have been previously used. Although SATA disk drives still do not offer the same level of performance as an enterprise SAS or SCSI drive, they are ideal for many environments where cost and capacity are the primary factors. SAS disks, on the other hand, offer 15K RPM rotational speeds (versus 7,200 RPMs with most nearline and desktop SATA disks) providing significantly lower latency, greater IOP capability and up to 50% greater sustained throughput per drive than a typical SATA disk. SAS disks are also designed to withstand higher rotational vibration interference (RVI), with higher mean-time-between-failure (MTBF), and lower bit error rates (BER) even in servers that work around the clock. 1. M. F. Arlitt and C.L. Williamson, Workload Characterization: The Search For Invariants, from the Proceedings of The 1996 ACM SIGMETRICS International Conference on Measurement and Modeling of Computer System.

2 2 For latency-sensitive, transactional-storage environments, a SAS disk configuration can offer up to four times the random I/O performance of a comparable SATA configuration. However, for many applications, SATA drives can deliver satisfactory performance. 2. Storage Server Applications and Usage Models Although every storage server is unique, there are many common characteristics among the most popular usage models, as shown in Fig. 1. Today s high-speed world of e-commerce requires storage that can service multiple customer web requests with the lowest possible latency. Both static and dynamic workloads are comprised almost exclusively of read requests with generally random I/O distributions. Studies have shown that approximately 84% of web server request sizes fall below 16KB, while the remaining 16% is evenly distributed from 32KB to 1MB (consisting primarily of video, audio and images). 2 The best web server performance can be achieved with RAID controllers with a dynamic caching policy that reduces the controller overhead when dealing with overlapping read and write requests. RAID enhances web server performance by distributing the requests across all the participating drives, significantly increasing performance while also improving availability and reliability. OLTP Our digital economy has become more reliant on storage systems for archiving online transactions and vital records such as database applications including decision support/data warehousing, web-based e-commerce and business reporting. Transaction processing and database query I/O requests tend to be small, generally less than 16KB, requiring a read of the original value, followed by an update, write and verify operation. Because transaction servers are highly sensitive to response times, the ability to preserve data integrity by maintaining inorder execution (to ensure atomicity) of requests for a mixed read/write workload, while minimising controller overhead, is key to a high-performing database. File servers present a special challenge since user requests tend to be scattered across the span of the disks, with distinct hot spots. These hot spots, which typically contain file information structures, open-file updates, page swapping regions and other frequently accessed data, benefit from effective array caching. The busiest file servers need to service thousands of requests each second. Ideal RAID controllers for file serving demonstrate the ability to handle a greater number of user requests, which translates to lower response times on even your most demanding file servers. The nature of the workstation environment consists primarily of a single user running multiple applications, which operate in such a way as to leverage the virtual memory subsystem (VMS). workloads are predominantly a mix of random accesses of blocks that match the VMS s page granularity, with a sequential component of read and write disk stores once the task is finished. In this case, since the user is essentially waiting for the disk operation to complete before being able to continue, latency again is very important. 3. Adaptec Controllers are Optimised for Your Real-World Workloads Adaptec has addressed the most common workloads generated by today s applications and optimised our advanced data protection RAID software to give the best overall performance. In fact, as shown in the charts in the next section, Adaptec controllers provide the ability to handle an impressive 30-50% more user requests than the competition. Adaptec RAID Code (ARC) is designed with dynamic algorithms that can adjust caching and code flow policies to produce optimal performance based on I/O characteristics and statistics, without user intervention. As a result, you can reduce the latency that slows workstation usage as well as handle the largest number of file serving user requests, the overlapping read and write requests of web serving and the in-order execution required by OLTP, while maintaining the best possible performance. Measurement I/O Characteristics Typical Applications OLTP Typically 2KB 16KB request sizes; read, modify, write, verify operations Databases (SAP, Oracle, SQL), Servers resulting in 2 reads for every write; primarily random accesses; large number of concurrent requests. s Primarily small to medium request sizes; 80% sequential and 20% random; Business Productivity, Scientific/Engineering Applications generally 4 reads for every write operation; 1 4 concurrent requests. Wide distribution of request sizes from 512B to 512KB; primarily random accesses; large number of concurrent requests during peak operational periods. Web Services, Blogs, RSS Feeds, Shopping Carts, Search Engines, Storage Services Moderate distribution of request sizes from 4KB to 64KB, although 4KB and 64KB comprise 70% of requests; primarily random; generally 4 reads for every write operation; large number of concurrent requests during peak operational periods. Fig. 1 Characteristics of common storage server workloads and applications. File & Printer Servers, (Exchange, Notes), Decision Support Systems 2. Dave Reinsell, IDC, State of the Storage Industry presentation

3 Unified Serial Controllers Enhance Performance Another key feature that allows Adaptec controllers to enhance your performance for SATA and SAS drives is our Unified Serial Architecture.

3 3 Unified Serial Controllers Enhance Performance Another key feature that allows Adaptec controllers to enhance your performance for SATA and SAS drives is our Unified Serial Architecture. Adaptec Unified Serial RAID controllers support both SATA and SAS disk drives and improve I/O performance whether you take advantage of low-cost SATA disks or high-performing, reliable SAS disks, or both, in a tiered storage solution. Built on SAS technology, they bring many improvements to the use of SATA disks, including scalability to 128 storage devices, which is not possible with SATA controllers. 8 & 16 SATA Drives PCIe The performance of the Unified Serial Adaptec Serial Attached SCSI RAID 4805SAS is shown below in a RAID 5 configuration with eight SATA II nearline disks against offerings from Promise, 3ware and Areca, and a SAS RAID controller from LSI. The greatly out-performs the competition in these workload measurements. In web server environments, Adaptec can handle 62% more web requests than the Areca 1220 and 53% more web requests than the. While the 3ware 9590SE-16ML competes well against the Adaptec controller, it doesn t offer the flexibility of deploying SAS disks, nor external connectors to support rapidly growing storage needs. In fact, when buying SATA-only controllers, IT administrators will need to purchase a controller with enough connectors to support their future needs. Unlike Adaptec Unified Serial controllers, 3ware, Promise and Areca SATA controllers have only internal connectors, requiring risky hardware reconfigurations and server downtime to add additional storage to the system. 8 SATA DRIVES - PCIe Fig. 2 Example of tiered storage built on Unified Serial Architecture. 3Ware 9590SE-16ML Promise EX16350 Areca Performance Analysis The following charts demonstrate the superior competitive performance of Adaptec controllers for common workloads. 8 SATA Drives PCI-X The Adaptec Serial ATA II RAID 2820SA exhibits the best performance of all the SATA controllers, out-performing LSI by as much as 63% per-cent. 8 SATA DRIVES - PCI-X Fig. 4 Eight-drive SATA RAID 5 performance of Adaptec RAID 4805SAS shown against 3ware, Promise and Areca SATA DRIVES - PCIe Adaptec 2820SA 3Ware 9550SX LSI 300-8XLP Promise EX8300 3Ware 9590SE-16ML Promise EX Fig. 3 Eight-drive SATA RAID 5 performance of Adaptec RAID 2820SA shown against 3ware, Promise and LSI Fig. 5 Sixteen-drive SATA RAID 5 performance of Adaptec RAID 4805SAS shown against 3ware, Promise and LSI.

4 4 Even in larger configurations shown below, Adaptec RAID 5 performance continues to scale as you add more disks. With the same 8-port controller, the performance scales from over 700 I/Os per second to almost 1,400 I/Os per second. Adaptec sets the standards in performance and scalability, delivering added value within a cost-sensitive environment. 8 & 16 SAS Drives PCIe While Adaptec controllers out-perform the competition in transactional environments with SATA disks, the story is even more compelling with SAS disks. The charts below show the same four workloads comparing an against two LSI SAS RAID controllers, the LSI8344ELP and the LSI8408E. Notice the dramatic performance of the in both eight- and sixteen-drive RAID 5 configurations. Fig. 6 Eight-drive SAS RAID 5 performance of Adaptec RAID 4805SAS shown against LSI. 8 SAS DRIVES - PCIe SAS DRIVES - PCIe LSI 8408E LSI 8408E Fig. 7 Sixteen-drive SAS RAID 5 performance of Adaptec RAID 4805SAS shown against LSI. SATA or SAS? Yes! With Adaptec Unified Serial controllers, the benefits of both low-cost SATA drives and high-performance SAS drives can be achieved with a single controller. No more dedicated hardware for specific applications. A single Unified Serial controller from Adaptec leverages both cost-sensitive, high-capacity environments and high-performance, high-availability environments. These benefits result in lower total cost of ownership, reduced training and support costs, decreased inventory costs associated with special purpose hardware, and improved scalability. Disk Technology 7200 RPM SATA 15K RPM SAS $ per GB $ $0.81 $ $6.87 Sustained Media Rate (MB/s) Maximum Typical Usages Media Serving, Video Surveillance, Medical Imaging, Reference Data, Content Creation, s s, , Databases, Transactional Servers, s Ideal Environments Bandwidth, Cost Sensitive Latency, Availability Sensitive Fig. 8 With Unified Serial controllers both high-capacity SATA drives and high-performance SAS drive can be used in a single system. Increased Value with Adaptec. It s More Than Just Performance. The Adaptec family of HBAs and RAID controllers, including the new Unified Serial product line, offer the most advanced feature set and highest performance of any brand in the market. In addition to the standard RAID levels of 0, 1, 5, 10 and 50, many of these controllers also integrate the Adaptec Advanced Data Protection Suite, with features including: Hot Space (RAID 5EE) Provides RAID 5 data protection with a hot spare while allowing all the disks to be used for data storage. Dual Drive Failure Protection (RAID 6, 60) Survive two disk failures without losing data. RAID 6 can raise SATA disks to enterprise-class reliability. Striped Mirror (RAID 1E) Extends RAID 1 across an odd number of drives. Copyback Hot Spare Designate a hot spare in your cabinet, and when a failed drive has been replaced, data is automatically copied from the hot spare to the restored drive, allowing the hot spare to remain in the same spot. Snapshot Backup This optional feature enhances the management of data backups with point-in-time snapshots. Adaptec Storage Manager (ASM) adds even more value with a one-view GUI that simplifies the management of all Adaptec storage on the network from a single console. Online help, physical and logical views, configuration wizards, and event scheduling and notification make ASM the most comprehensive, easy-to-use RAID management tool on the market.

5 5 5. Summary As companies become more reliant on storage, performance and availability are absolutely essential to keep businesses operating efficiently. From the top web server throughput in the industry, to the fastest response times for transactional servers, you can be confident you have the performance edge with Adaptec RAID controllers. Whether you choose Adaptec SCSI, SATA or Unified Serial (SAS) RAID controllers, you ll find them seamless, comprehensive, robust, easy to use and incredibly fast. Adaptec RAID controllers are designed to perform well in real workload environments, because ultimately what matters is a responsive database, being able to keep up with your company s traffic, completing backups within your window or viewing your video without dropping frames. Quite simply, Adaptec RAID controllers do real work, real fast! 6. System Setup RAID Controller BIOS Firmware Driver Stripe Size RAID Caching Policy Utility Adaptec SAS RAID 4805SAS 5.2-0[11564] 5.2-0[11564] 5.2-0[11518] 256KB Write Cache Enabled/Read Cache Enabled Adaptec SATA RAID 2820SA 5.2-0[11564] 5.2-0[11564] 5.2-0[11518] 256KB Write Cache Enabled/Read Cache Enabled LSI 8408E SAS MFI vmt KB Read Cache Normal, SAS MFI vmt KB Read Cache Normal, LSI 300-8XLP H D KB Read Cache Normal, Adaptec Storage Manager Adaptec Storage Manager MegRAID Storage Manager v MegRAID Storage Manager v None Areca a KB Write Cache Enabled Areca HTTP Promise EX KB Performance WebPAM Promise EX KB Performance WebPAM Promise EX KB Performance WebPAM Ware 9550SX-8LP BE9X FE9X KB Write Cache Enabled 3DM 2 3Ware 9590SE-8ML BE9X FE9X KB Write Cache Enabled 3DM 2 3Ware 9590SE-16ML BE9X FE9X KB Write Cache Enabled 3DM 2 Windows 2003 Enterprise Edition (SP1 + all patches as of 27/09/06) SuperMicro X6DH8-G2 with 2GB DDR2-400 ECC Memory, 2x 3.6GHz Xeon (HT enabled) IOmeter Build Seagate ST336754SS SAS 3.0 disks (write cache enabled) Seagate ST N SATA-II disks (write cache enabled) Adaptec, Inc. 691 South Milpitas Boulevard Milpitas, California 95035, USA Tel: Fax: Adaptec UK Tel: +44 (0) Web: presales_uk@adaptec.com Copyright 2007 Adaptec, Inc. All rights reserved. Adaptec, the Adaptec logo, Snap Appliance, the Snap Appliance logo, Snap Server, Snap Disk, GuardianOS, SnapOS and Storage Manager are trademarks of Adaptec, Inc., which may be registered in some jurisdictions. Microsoft and Windows are registered trademarks of Microsoft Corporation, used under licence. All other trademarks used are owned by their respective owners. Information supplied by Adaptec, Inc. is believed to be accurate and reliable at the time of printing, but Adaptec, Inc. assumes no responsibility for any errors that may appear in this document. Adaptec, Inc. reserves the right, without notice, to make changes in product design or specifications. Information is subject to change without notice. P/N: UK Printed in Europe. 01/ _1.5

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