Storage Control Solutions from Intel Form Cornerstone of Digital Home

Developers face challenges in digital rights management, network bandwidth, content storage, interoperability, dynamically changing environments, and distributed control.

By C.C. Hung and Richard Schmitt

Embedded devices are quickly becoming faster, cheaper, and capable of integrating more peripheral functions. As a result, traditional product categories are merging to create unique, multifunctional, and convergent devices. These devices address the consumers’ desires for accessing information, education, and entertainment content. Consumer-electronics devices are thus moving into a whole new age of computing in terms of how digital content (data, voice, audio, and video) can be transferred and shared between devices with unprecedented control, convenience, and security in mind.

The connected (digital) home is a new, evolving consumer market segment in the electronics space. It is driving new technologies, standards, and innovative products aimed at delivering digital content over home networks. Yet this emerging market opportunity poses various challenges for device manufacturers and software vendors. Among the common challenges seen in the deployment of digital-home solutions are digital rights management, network bandwidth, content storage, interoperability, dynamically changing environments, and distributed control. Universal Plug-and-Play1 (UPnP), Common Internet File System2 (CIFS), Network Attached Storage (NAS), and media server technologies have been developed on the Intel® 80219 general purpose PCI processor and Intel® IOP321 I/O processor to create a new class of home servers based on the Intel storage controllers. These solutions are destined to become successful and pervasive in the next era of consumer applications.

Home Servers
The digital home also has created a new type of product, which is often referred to as a NAS media server. This device reliably stores a massive amount of content that can be accessed either through players or directly from PCs using traditional file-sharing capabilities. In addition to storing digital-media content, users can store their tax returns, e-mail, spreadsheets, and other documents. The Figure displays typical products for the digital home. A digital media player similar to the D-Link (www.dlink.com) DSM-520 Wireless HD Media Player is connected to a Sharp (www.sharp.com) LC-32D4U HDTV using a standard HDMI connection. A Blue Peach (www.bluepeach.com) Blue Stream BPMS-120 Media Server with 500 GBytes of digital content is located somewhere within the home. The link between the media server and player is a 54-Mbps wireless 802.11g connection. Using this simple configuration, a person sitting in front of the TV can view all of the pictures uploaded from the digital cameras, listen to any audio uploaded from a CD or downloaded from the Internet, and view any movie stored on the media server. As more consumer-electronics devices become available for the digital home, the variety and capabilities of these products will continue to increase. The result will be robust digital-entertainment environments.


Digital-Media-Server Technologies
In the digital-home architecture, a digital media server stores and catalogs digital content. It allows access to that catalog for searching and browsing. In addition, it serves up the content to digital media players on demand. A media server consists of a number of required and optional sub-components that deliver the various functions of the content-storage server. In the Blue Peach Solar Home Server, the Intel 80219 general purpose PCI and Intel IOP321 I/O processors are used. This platform comprises the 400-MHz, high-performance Intel XScale® technology-based cores and integrated Gigabit Ethernet controllers. It enables the easy integration of SATA controllers. The home server is targeted to the Mentor Graphics (www.mentor.com/embedded) Nucleus real-time operating system (RTOS) including the real-time kernel and file-management and networking-middleware products. The Nucleus RTOS platform supports home-server and networking applications with its reliability, high performance, wide range of supported devices, protected design, and security features.

Obviously, a media server must have access to a storage medium. It has to be able to read and write content to that storage medium. For a media server, there are a number of choices for storage technology and file-system software. Logical choices for a drive subsystem include IDE, SCSI, or SATA. The tradeoffs are primarily between speed, cost, capacity, and mechanical issues.

The IOP321 and 80219 controllers are fully integrated with the Intel® 31244 PCI-X to Serial ATA Controller. SATA is the ideal connectivity architecture for home-server storage due to its hot-pluggability and high-capacity, high-performance, and low-cost subsystem characteristics. The 80219 design supports two 31244 SATA controllers while the IOP321 design supports four SATA controllers. Each controller supports up to four SATA drives, which results in a total connectivity of eight drives for the 80219 and 16 drives for the IOP321.

The reliability of the storage subsystem also is a design concern. Data backup in the home is typically rare. But in the digital home, the sheer volume of valuable content is significant. A loss of this content would be disruptive. It also would invalidate the architecture in the consumer’s mind. To alleviate this concern, a number of RAID strategies can be deployed. The simplest and most common of these strategies is RAID 1. Here, data is mirrored on a separate disk. If a drive fails or a block cannot be read on one disk, the data should still be available on the mirror. If the block can be recovered, the original data can be brought back in synch. If a disk needs to be replaced, the disk can be “hot plugged.” A new drive can then be inserted in its place. All data from the mirror can be recovered to the replacement disk.

A more sophisticated and cost-effective RAID solution is RAID5. It uses a parity disk along with two or more data disks arranged in what is termed a “stripe.” The number of data disks that make up a stripe is implementation-specific. Generally, however, the optimum tradeoff between reliability and data storage results in four data disks and one parity disk per stripe. Interestingly, RAID1 (mirroring) is a special case of RAID5 in which there’s one parity disk and one data disk. Because there’s only one data disk, the parity disk ends up containing an exact copy of the data on the data disk.

The Intel 31244 SATA controllers are ideal for RAID implementations because of their support for hot-pluggability. The Nucleus FILE provides drivers for the Intel 31244. In addition, the Nucleus FILE architecture supports the notion of layered file systems and drivers. It is therefore well suited for supporting a RAID driver layered between the upper-layer file system and lower-layer SATA driver.

The storage enclosure used is key in implementing an effective storage subsystem. Platforms like the Solar Home server utilize an enclosure based on the StorCase InfoStation 1U SATA RAID enclosure. This enclosure supports 10 2.5-in. hot-pluggable SATA drives. These 10 drives can be arranged into two five-drive RAID5 stripes. The 80219 will support one RAID5 stripe while the IOP321 will support two stripes. The state of the art in 2.5-in. drive capacity is 200 GBytes, resulting in a top capacity of 1.6 TBytes in a fully protected system.

The choice of file system also is an issue in designing an effective storage subsystem. A number of file systems are available that offer differences in performance, reliability, and capabilities. Some common file systems are shown in the Table. Although FAT32 may be the simplest to implement, it has the lowest reliability and performance. NTFS is a licensed format of Microsoft. EXT2 and EXT3 may be the most logical choices due to their high reliability and performance. Other file systems are available as well and should be considered.

Networking Technologies
The connected home depends on the ubiquitous deployment of wireless and wired home networks. This infrastructure is predominantly based on Ethernet and IP standards. The digital home is designed to take advantage of this infrastructure. To deploy a digital-home application within a device, a standard TCP/IP stack can be used. It should include ARP, DHCP, IP, TCP, and UDP. Depending on the serviceability strategy, other protocols may be relevant (TFTP and Telnet). If media streaming is implemented, the RTP and RTSP protocols may be relevant as well.

An addition to standard IP protocols has been adopted by the DLNA. Called Auto-IP or ZeroConf, it’s a cross between DHCP and ARP. This protocol allows a device to determine a dynamic IP address in the absence of a DHCP server. All digital- home devices should support Auto-IP. The Nucleus NET TCP/IP stack supports it while providing hooks to applications in order to manage IP-address assignments and conflicts.

Clearly, a network interface needs to be chosen and supported as well. Generally, a 1080i HD video stream encoded as MPEG23 or WMV requires under 10 Mbps. It follows that a 100-Mbps wired network or 54-Mbps 802.11g wireless network will support multiple HD video streams.

The Intel 82546 dual-port Gigabit Ethernet controller is used in the Solar Home Server. With the Intel 82546, the home server can scale to very high network bandwidths. Yet it also is able to serve as a media gateway with both a public- and private- network interface. The 82546 has the ability for TCP/IP checksum offloading as well. The Mentor Graphics driver supports the advanced features of this controller.

Convergence Enables Digital Home
The consumer-electronics industry is leading the development of new and innovative products. These products leverage the convergence of device technologies. As a result, consumers can receive digital entertainment conveniently, comfortably, and securely throughout their homes. The collection of these technologies enables advanced consumer applications that will enhance the consumer’s experience. At the same time, those technologies will allow the flexible storing, sharing, and playback of content throughout the home. The technologies are architected so that there’s flexibility in the design of new devices. This flexibility creates opportunities for product differentiation.

The digital home is the first step in an emerging device revolution in which devices cooperate and applications are distributed throughout the home. The underlying protocols and technologies of the digital home will provide new functions and advanced features that will change the way people interact with devices throughout the future. The Intel 80219 and IOP321 processor-based platforms are ideal starting points for advanced home servers. They will enable enterprise-class storage for the home.

References
1 Jeronimo, Michael, and Weast, Jack, UPnP Design by Example: A Software Developer’s Guide to Universal Plug and Play, Intel Press, 2003.
2 Hertel, Christopher R., Implementing CIFS: The Common Internet File System, Prentice Hall, 2004.
3 MPEG-21 Overview (version 5.0), ISO/IEC JTC1/SC29/WG11/N5231, Motion Pictures Export Group, 2002; available from www.chiariglione.org/mpeg/standards/mpeg-21/mpeg-21.htm.



C.C. Hung is the Product Marketing Manager for the consumer- electronics market in the embedded- systems division of Mentor Graphics. Hung has an MS in Electrical and Computer Engineering from the University of Texas at Austin, an MS in Mechanical Engineering from Pennsylvania State University, and a BS from the National Central University in Taiwan. He can be reached at cc_hung@mentor.com.

Richard Schmitt is the CEO and CTO of Blue Peach, which he founded in 2002. A published author and contributor to several standards initiatives, Schmitt graduated from Johns Hopkins University with a BA degree. He can be reached at rschmitt@bluepeach.com.