Network attached storage (NAS) boxes and storage-area networks (SANs) are common in the corporate world, providing a range of storage features. In the future, there likely will be a NAS box in every home as streaming multimedia becomes more common.
The potential for home use is changing the kinds of features that are found within NAS boxes. This in turn is changing the types of platforms needed to handle the growing number of services such as multimedia transcoding. Likewise, other platforms such as Blu-ray disk players are starting to incorporate these features, blurring the lines between set-top boxes and NAS devices.
Companies like Applied Micro and PLX are targeting this space with multicore chips specifically designed for the storage market. For example, PLX’s NAS7820 dual ARM11 core chips (Fig. 1) incorporate enough power to handle multistream transcoding for NAS-related chores in addition to redundant array of independent disks (RAID) storage chores. The NAS7820 reference design board (Fig. 2) supports dual SATA, dual USB, and dual Gigabit Ethernet interfaces. A built-in TCP/IP offload engine (TOE) supports the reference design board.
The eight-channel, low-latency buffered DDR2 memory controller handles bandwidth bursts up to 12 Gbits/s. Multiport SRAM supports the eight separate DMA engines in multiple bus masters in addition to the dual-core processor. Hardware acceleration for 128/256-bit AES encryption, RAID support, and network support allows the platform to handle a range of applications at the same time. The system-on-a-chip (SoC) also supports NAND and NOR flash.
Applied Micro, formerly AMCC, has been delivering PowerPC-based solutions for the storage market for many years (see “Smaller, Power-Packed Hi-Def Designs Rule This Year’s ESC”). It has been a leader in the NAS market using its family of single-core and multicore 4xx processors. Its latest package, the Applied Micro NAS Reference Design (Fig. 3a), is based on the Primo board (Fig. 3b), which supports this processor family.
The NAS Reference Design supports up to four SATA drives in addition to eSATA and USB devices. The board has a mini-PCI connector for expansion. It supports JBOD (Just a Bunch Of Disks) and RAID 0, 1, 10, 5, and 50 with hardware acceleration. It also has built-in security and encryption support. Like the PLX solution, it can handle multiple HD streams.
Intel’s IA-32 processors will be found in a range of third-party platforms. The new Core i3 and i5 in addition to the Atom line are ideal NAS hosts depending upon the kind of application. AMD’s Geode LX NAS RDK targets low-cost, low-power NAS applications (see “Cautiously Optimistic Exhibitors Revisit ESC In 2007”). The Geode LX 800 uses only 0.9 W and handles SATA and Gigabit Ethernet using the companion Geode CS5536 chip.
VIA Technologies uses a slightly different approach with the ARTiGOA2000 NAS platform, which is based on a Nano-ITX-based board running the 1.5-GHz VIA C7 processor (see “Nice NAS”). It is sold as a bare-bones NAS device by companies like Logic Supply that can also customize it by adding drives and flash memory. The Nano-ITX board accepts a Compact Flash card, and Logic Supply has a version of the FreeBSD-based FreeNAS that boots from a 1-Gbyte flash card.
The latest device from VIA Technologies, the VIA M’serv (Fig. 4), adds a second Gigabit Ethernet connection. This dual network connection is becoming more common and shows up in other platforms like the PLX reference design. The second port can be used for gateway applications, but it can also be useful for backup and streaming applications.
For example, a network-based HDTV tuner like the dual-channel HD Home-Run (Fig. 5) from SiliconDust can be used off one network interface while the other streams recorded content to a network-enabled HDTV. In this case, the NAS device needs to run a background personal video recorder (PVR) application such as the MythTV back end (see “Hitting An HD HomeRun”).
Of course, configuration can be a challenge since a PC with a Web browser is likely to be found on the HDTV side, but many applications like MythTV handle device configuration from the server. Alternatively, the NAS device can be configured as a router providing direct access to the devices on the other network segment.
SMALLER NAS DEVICES
The hard drives that are used to provide storage dictate most NAS device design. This typically means one or more 3.5-in. or 2.5-in. hard drives. The M’serv accepts a pair of 3.5-in. drives for a current upper capacity of 4 Tbytes using drives like Seagate’s 2-Tbyte Barracuda (see “Seagate Delivers 2-Terabyte Hard Drive”). The power supply and Nano-ITX board fill up the rest of the space.