A few days ago i received the new D-Link DNS-320 Sharecenter Pulse. In this Post i want to show a few pictures which were take while unpacking the device. The content of the Box offers the Device itself, two power plugs, a small power supply and a networking cable. Additionally there is a CD with useful tools and the manual on it.
If you want to install the HDDs, you simple slide the top of the NAS back and pull the HDDs down into the case:
To avoid confusion, D-Link has labeled the slots with “L” and “R”. At the front the USB-Port is hidden. Additionally there is a button which transfers the data on the USB-Stick to the NAS if pressed.
Apart from a power button and some status LEDs on the front, the CH3SNAS has the following external interfaces:
a DC power suppy input This plug is for the supplied external power supply which is rated at 5 Volt by 3 Amps plus 12 Volt by 3 Amps. This 50 Watt rating suggests that the CH3SNAS uses roughly half of the peak power of high-end laptop. Most of this power will be used by the drives (when these are active).
Gigabit Ethernet port This is for connecting the NAS to your local-area network. The port supports 10 Mbit/s, 100 Mbit/s and 1000 Mbit/s ethernet. In practice you are unlikely to see speeds above 200 Mbit/s – likely due to performance limitations of the CH3SNAS.
a single high-speed (480 Mbit/s) USB 2.0 port This port is only used to drive a printer. Other peripherals are not supported by the standard software. You cannot use the port to connect the CH3SNAS to a PC which acts as host without drastic software changes (a SAN is not a NAS; USB master/slave distinction; Windows does not support access to Ext2 formatted drives).
The central processor in the CH3SNAS is a Marvell Feroceon 1850 processor core inside Marvell’s Feroceon 88F5182 chip “for Networking and Storage”. This core is compatible with the ARM v5TE instruction set architecture (often informally known as ARM9). Although some web sites state that this processor is an XScale processor, this is not inline with Marvell’s documentation and with the table provided by debug tooling specialist Lauterbach. See also Output of /proc/cpuinfo.
In Linux kernel circles, the chip is often referred to as Orion after internal code name. Marvell has been very active recently to get the mainstream Linux kernel to support this architecture.
This 88F5182 features a general-purpose CPU (the Feroceon), memory interfaces, as well as a dual port SATA controller, two USB ports (one is unused), and the digital circuitry (“MAC”) required for Gigabit Ethernet. Thus if we compare the 88F5182 to a hypothetical single-chip NAS, it lacks memory (which is normal), analog circuitry (“PHY”) needed for the Gigabit Ethernet port and it requires the usual handful of smaller support devices. The 88F5182 also provides PCI and PCI Express support, but neither is utilized in the CH3SNAS.
Gigabit Ethernet Tranceiver
The physical layer for Gigabit Ethernet (as well as 10 and 100 Mbit/s Ethernet) is provided by a separate Marvell 88E1111 chip. This converts (differential) serial signals into lower speed parallel data for further processing by the MAC layer in the 88F5182. The serial input/output pins are not directly connected to the RJ45 connector, but pass via a transformer (“magnetics”). This is probably to accomodate for differences in common mode level between two computers, and possibly to provide a degree of electrical safety.
The CH3SNAS has 64 MBytes of volatile Double Data Rate (DDR) DRAM. The DRAM is not upgradeable as both 256 Mbit Nanya NT5DS16M16CS-6K chips are soldered to the main circuit board.
DRAM is needed to run the software (variables, state, stack). It is also used to buffer data for the various servers (e.g. files to hard disks gets buffered in memory and then sent via Serial ATA drives). It also contains a RAMdisk which behaves like a hard disk, but looses its data when the devices is turned off.
The CH3SNAS has 8 MBytes of Flash memory (Spansion S29GL064A90TFIR4) to hold the firmware and its support files (using a compressed, read-only file system).
Regardless of whether the CH3SNAS is on or off, a real-time clock chip (the ST M41T80) is powered up from a battery and keeps track of time. This is similar to how PCs work and is needed, for example to execute tasks at predetermined times/dates. Unfortunately, the real-time clock cannot wake up the CH3SNAS at some predetermined time. See Tutorial on NTP-Timesynchronization for information about accuracy of the time function available to software and how to improve that by synchronizing across the network.
The real-time clock is powered by a 3V battery. The battery should last a few years. If you ever find that the NAS ever looses track of time when you turn if off or disconnect the power, you should replace this battery.
Comparison to a PC
No display or sound
If we compare this to what people typically expect in a stand-alone computer, there is a no display or option to connect one (compensated by browser-based configurability), there is no sound output or option to add sound (compensated by a few LEDs) and no direct keyboard or mouse input possible (compensated by running a web browser on a “real” computer when you need to configure the CH3SNAS).
There is also no way to add or extend the memory inside the system. This is normally not needed. But can be critical for advanced users because the embedded software inside the system does not (unlike personal computers)use space on the hard drive as extra “virtual” memory. All software is expected to be fully operational – even if no drives are inserted.
During normal operation, the CH3SNAS has 0.5 or even 1 GBytes of virtual memory. This “swap” space on the hard disks (0.5 GBytes/drive) is used to temporarily store stuff that doesn’t fit into DRAM. This is pretty normal for Linux, but is a bit special because under some conditions (e.g. no drives are available yet) the same software needs to be able to run without virtual memory.
A more fundamental difference between a personal computer and an appliance like the CH3SNAS, is that users expect to be able to easily install new software (e.g. a game) on their personal computer. The CH3SNAS is an embedded computer in the sense that it comes with pre-loaded software, and you are unable to easily add more software: the system is closed and optimized for a particular set of tasks. Fortunately there are ways for advanced users to add more software (see fun_plug within the constraints of the memory limitations.
The CH3SNAS is essentially a small file server which you connect to a local TCP/IP network via an ethernet cable. In a home network, the CH3SNAS will typically be connected via a UTP cable to a router. The CH3SNAS can contain up to two 3.5 inch SATA drives (which can be sold bundled with the actual CH3SNAS). The drives can have any capacity (typically 0.2-1 TBytes/drive). If two drives are used (for extra capacity or to enable RAID 0 and 1 modes), they do not need to have equal storage capacity or be of the same brand.
The CH3SNAS is internally a small, networked Linux computer with one or more shared (logical or physical) network drives. The CH3SNAS is primarily intended to store files that can be accessed by a computer on the local network.
One specific application highlighted by the vendor is to stream audio or video from the CH3SNAS to other networked devices such as laptops or a Playstation 3. Alternatively it can centrally store media, which can then be copied to smaller portable devices (Conceptronics markets their storage product line with the slogan Grab’n’Go).
Files can optionally be accessed across the internet (via an FTP server, which is disabled by default for security reasons). As a bonus, the CH3SNAS can also act as a print server, thus converting a printer with a USB port into a printer than can be shared across the local-area network.
The CH3SNAS caters to a wide range of users:
average home PCs users with a wired or wireless network
users interested in computing technology (and thus interested in trying out more advanced featues)
tweakers who are willing to spend significant amounts of time to tune/adapt the (and may thus actually extend the system – which is internally Linux-based).
More information on target users, target usage, and interoperability with various operating systems can be found in the article on Usage-Scenarios.
Hard disk configurations
The CH3SNAS can be operated with a single or dual 3.5 inch hard disk of any capacity or brand. When the system is initialized, the user has the option of creating partitions (volumes) which can be on a single disk or span both disks. A list and discussion of the possible storage configurations can be found in Configuration Options.
Externally, the CH3SNAS has a Gigabit Ethernet connector, a USB port for connecting a printer, a connector for the supplied power supply, a single on/off button, four status LEDs and a somewhat hidden reset button.
The internals obviously consist of the hard disks themselves (which may come with the CH3SNAS, but can also be purchased seperately) and a circuit board that houses the processor and memory chips which form the small computer which contols the hardware and provides the numerous software features. Unlike destop PCs or laptops, the computer is not hardware upgradeable. The central chip is a complex System-on-Chip manufactured by Marvell (Marvell Feroceon 88F5182). More hardware details and photos of all key components can be found in Hardware.
The software running on the embedded processor core is mainly needed to support the following features:
SMB/CIFS (file server for a LAN)
FTP (file server for usage across the Internet)
Print server (connect a USB printer to the network)
uPnP (multimedia server)
iTunes server (Apple’s multimedia server)
More software details on these protocols and a more extensive list of modules can be found in [[CH3SNAS:Software]] [[XXX]]. The software also includes a configuration interface which be access via a web browser (similar to the way routers are typically configured).
This Linux-based software is stored in an on-board non-volatile Flash memory which allows the CH3SNAS to boot even when the hard disks are not yet operational. The softwarecan be updated to newer firmware versions via the web-based configuration interface. In addition, the CH3SNAS (as well as various similar devices) have options to allow the more technically inclined to add scripts or even additional servers without having to recompile code or even without having to modify the content of the Flash (via the so-called fun_plug technique).
More detailed versions of the above abridged sections can be found on separate pages in this blog:
Usage – target users, target usage, and interoperability