Storage Device Dynamics for Enterprise Datacenters – An IDC Perspective*

Author: John Rydning, Research Director, Hard Disk Drives

Storage device options continue to broaden for disk storage system OEMs and end users. For enterprise applications, hard-disk drives (HDDs) are now available in several form factors, configured with parallel SCSI, Fibre Channel, Serial ATA (SATA) or Serial Attached SCSI (SAS) interfaces. An increasing number of solid state drives (SSDs) are now also shipping for enterprise applications. DRAM-based SSDs have for many years satisfied the needs of very high performance, latency-sensitive environments, but at a high cost. Now, with the price decline in NAND flash and advances in technology, NAND-based SSDs have a growing opportunity in the datacenter. Similar to HDDs, flash-based SSDs are offered with several interface options.

Today’s diversity of storage device options for the datacenter contrasts sharply with the limited selection available just five years ago. Consider the changes that have taken place just with hard disk drives. In 2003, essentially two HDD form factors serviced the large percentage of enterprise datacenter storage demands: 3.5 inch 10,000 rpm and 3.5 inch 15,000 rpm HDDs. Today, in addition to these 3.5 inch enterprise class products, the HDD industry also ships 2.5 inch 10,000 and 15,000 rpm enterprise-class small-form-factor (SFF) drives. Collectively, IDC classifies these drives as performance-optimized HDDs. By 2009, 2.5 inch performance-optimized HDDs will out-ship 3.5 inch products.

HDD vendors have done an admirable job with increasing the average capacity of performance-optimized disk drives, but the growth rate is slowing. At the same time, 2.5 inch performance- optimized HDDs have less storage capacity than 3.5 inch drives due to smaller diameter disks, and lower maximum number of possible disks per drive. Given the migration to 2.5 inch enterprise SFF HDD products, the resulting overall average capacity of performance-optimized drives shipping to enterprise applications has remained relatively flat over the past few years.

Meanwhile, IT managers are faced with the dilemma of how to meet TB storage growth requirements of greater than 50% per year. Of course, one solution is simply to increase the number of HDDs per array, arrays per system, or number of systems per data center in order to reach the required amount of capacity. Instead, the HDD industry responded by delivering high capacity drives that store 3-4x more data than traditional performance-optimized drives, and are suitable for 24 x 7 use in rackmount environments. Use of these capacity-optimized drives helped IT managers to meet storage growth requirements, and resulted in a steady increase of the average HDD capacity shipping to datacenters.

Capacity-optimized drives will increasingly penetrate the data center as users learn how to better leverage these storage devices. In 2007, roughly 10.8 million capacity-optimized HDDs shipped in datacenter storage solutions. Over time, IDC expects a growing percentage of TBs will be stored on capacity-optimized disk drives. Figure 1 delineates this dynamic.


Figure 1: Datacenter Dynamics for HDDs, 2005 to 2011
Source: IDC, 2008


Meanwhile, there has been a growing disconnect between the I/O capabilities of the CPU in servers or controllers in storage systems, and HDD performance. To highlight this further, one need only consider a few of the various techniques that are employed today to increase storage performance such as striping data across multiple disks, using faster spin-speed HDDs (15,000 rpm versus 10,000 rpm), or even short-stroking the disk drive (using only the outer tracks of the disk where sequential data rates are fastest).

Generally, SSDs have much higher I/O capabilities than hard disk drives. When leveraged properly, SSDs can accelerate an entire enterprise system by ensuring that the I/O capability of the storage devices is in balance with the rest of the system. IDC believes that enterprise storage applications can benefit from the use of SSDs. In particular, certain storage applications, requiring high input/output transactions per second (IOPS) to support the data architecture and performance requirements of the computer system, are candidates for SSD-enabled acceleration.

Meanwhile, IT managers also face a growing challenge with power and cooling. It is not easy to predict the exact cost of electricity, but it is easy to anticipate the direction – up. A number of strategies have emerged, and will continue to emerge, to help reduce the energy associated with storage. ‘Green’ requirements will undoubtedly set in motion greener storage solutions, including at the storage device level.

Taken together, the result is a challenging environment for product positioning by HDD and SSD vendors. There are myriad storage device options available to customers. Some may employ a combination of performance-optimized and capacity-optimized HDDs, while some may choose to leverage SSDs and capacity-optimized HDDs.

Given the storage device options available today and in the near future, the permutations of storage systems configurations is almost mind-boggling. Nevertheless, within this environment, standardized solutions are needed wherever possible to achieve economies of scale necessary to help IT managers cope with rising storage costs.

Rapid Serial Interface Adoption

Amidst the confusion with device proliferation is one certainty: storage devices, HDDs and SSDs included, are increasingly migrating to standardized serial interfaces. Historically, storage technology or form factor transitions in the enterprise take time, interfaces included. But in comparison to other relatively recent technology transitions in the enterprise, the migration from parallel SCSI to SAS technology has been relatively quick. Figure 2 shows the HDD transition to SAS for performance-optimized drives based on HDD shipments from 2005 to 2007.


Figure 2: Enterprise-Class HDD Shipments, Percentage by Interface – All Form Factors
Source: IDC, 2008


In addition to the rapid transition to SAS for performance-optimized drives, the vast majority of capacity-optimized drives shipping for enterprise applications today employ the Serial ATA (SATA) interface. When accounting for all performance and capacity-optimized HDDs that shipped in 2007, more than 65% shipped with a serial interface (SAS or SATA).

A Bit More on SAS

The SAS interface was introduced in 2005 with a 3Gb/s data rate. The 3Gb/s data rate adequately supports the majority of requirements for storage system products in the market today. But storage system requirements change, and the SAS interface is being improved to meet these needs. The second generation of the SAS interface, dubbed SAS – 2, is now being readied for product launches later this year. SAS – 2 will have a 6Gb/s data rate, and be backward compatible with existing 1.5Gb/s SATA and 3Gb/s SAS/SATA products and infrastructure. The 6Gb/s SAS interface not only enables faster data rates, it also offers some new benefits and opportunities for enterprise applications, including the ability to spread I/O requests over a greater number of HDDs. It also provides a higher performance interface for future SSD devices designed with very fast I/O and data-rate capabilities. The 6Gb/s SAS interface also allows for the design of SAS storage solutions that could compete with storage systems currently leveraging the Fibre Channel interface. Figure 3 shows IDC’s expectations for the pace of the storage industry transition from 3Gb/s to 6Gb/s SAS.


Figure 3: IDC Forecast for SAS Interface Transitions in the Datacenter
Source: IDC, 2008


Amidst the multitude of transitions taking place for storage devices shipping to enterprise applications and the growing importance of dynamics such as power and cooling, HDD and SSD OEMs will have additional market dynamics to navigate. The success of certain storage system OEM product launches that integrate the various storage device types, along with storage device vendor pricing and product portfolio decisions, will all factor into specific HDD and SSD device demand. Despite the uncertainty within this environment, one element is certain: datacenter storage requirements for organizations continue to grow. Given the strong demand for storage capacity, the outlook for hard-disk drives is solid, and the industry will likely post successive years of record-breaking shipments and revenue.

*Excerpted from IDC Document # 212231, “Worldwide Hard Disk Drive 2008-2012 Forecast: Shrugging-Off Storage Technology Challengers, Document # 212736, “Worldwide Solid State Drive 2007-2012 Forecast and Analysis: Entering the No-Spin Zone”, and Document # 212714, “The Real Costs to Power and Cool All of the World’s External Storage”.


John Rydning is IDC’s Research Director for hard disk drives. Mr. Rydning provides insight and analysis on the hard disk drive industry for clients, HDD customers, investors, suppliers, and manufacturers. Specifically, Mr. Rydning analyzes HDD consumption patterns, HDD technology trends, and industry dynamics, and forecasts worldwide HDD industry shipments. Mr. Rydning also provides focused analysis on new HDD technologies, and competitive nonvolatile storage technologies and their influences on HDD industry dynamics.

Beyond his research responsibilities, Mr. Rydning provides custom research and consulting for IDC clients on industry trends, product requirements, and marketing strategies and is a frequent speaker at conferences and industry events.

Mr. Rydning has nearly 25 years of IT industry experience, including 20 years within the hard disk drive industry. He came to IDC in 2005 from Hutchinson Technology where he held several positions in marketing and materials management.

Mr. Rydning earned his bachelor’s of science degree in management from the Carlson School of Management at the University of Minnesota.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.