|Thecus N5550 NAS Network Storage Server|
|Reviews - Featured Reviews: Network|
|Written by Bruce Normann|
|Monday, 24 September 2012|
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Insider Details: Thecus N5550 NAS Server
The insides of these things are always more interesting than the outsides, at least to me. The N5550 comes apart very quickly and easily, with just three captive screws to be released on the rear panel. Once they're loosened, the outer shell slides off the front, revealing all the internal parts. Further disassembly requires a nutdriver or two, to remove the jack screws from the VGA D-Sub connector and to remove the power supply from the rear panel. The main controller board takes up the entire left side of the unit, and nearly everything is integrated on the one board, including all the front and back panel connectors. The two exceptions are the backplane where all the SATA connections for the drives are mounted, and the LED display and menu buttons from the front panel, which connect via ribbon cable. The main controller PC board slides into the plastic channels chassis at the top and bottom of the inner chassis. The board is not held in place by screws, but is captured so that it has no room to move.
Once you remove those couple of screws holding the rest of the chassis together, it comes apart in several smaller pieces. Most of the metalwork is permanently fastened together, or formed from a single sheet, so there are fewer loose components than I've seen on other NAS products. One design feature I was very impressed by was the bonding of the backplane PCB to a metal backing plate. The resulting sandwich is very stiff, which is exactly what you want for a backplane that has 1 kg HDDs occasionally slamming into it. The inner framework is a solid sheet metal assembly that is riveted together so that it stays dimensionally stable. The integrated power supply slides in from the rear and is held in place with four screws. The electrical output looks to be standard ATX connectors, which makes sense once you figure out just how close the overall architecture of this NAS is to a regular PC.
The main controller board is densely populated, not as much as a high performance video card, but the majority of the parts on the N5550 board are there to provide a unique set of functions. A video card PCB has at least 25% of the surface consumed by power regulation and distribution hardware. The main controller board and backplane connect with an x16 PCI Express connector located toward the rear of the controller card, between the CPU and the stacked I/O connectors. Noticeably absent from the main controller card is a power connector; all the electrical current comes through the PCI Express connector via the backplane PCB. Most of the current goes out to the hard drives, so it makes sense to land the power supply cables directly to that board, instead of here. The two passively cooled heatsinks cover the main chips supplied by Intel, the Dual-Core D2550 Atom CPU, and the ICH10R Southbridge that provides the SATA connections and the RAID logic. These two ICs do the bulk of the work for this NAS device; the only other chips that are even moderately stressed are the memory and the Ethernet controller.
The limited cooling required for the two hardest working chips on the controller board is made even more obvious once you remove the heatsink and see the type of thermal interface materials in use. The ICH10R Southbridge is thermally connected to the heatsink with that hard, plasticky material that we used to see on low-end video cards in the '80s and '90s. At least the assembly process and the viscosity of the material worked together to produce a thin interface layer. That's better than a 1mm thick layer of the good stuff, perhaps.
Speaking of cooling - I know I mentioned the fan before, but here it is mounted to the rear panel with the traditional, stubby, thread-forming screws that 90% of PC case fans are fastened with. It's a standard 92mm case fan, with 3-wire tachometer control and is modulated by the controller card. It was quiet and unobtrusive the entire time I had the unit under test, to the point where I never really paid any attention to it.
So far we've had a good look at what there is to observe as far as hardware goes, but let's dig down one more layer, down to the chip level where the technology really starts to get interesting. I love my shiny hardware just as much as the next person, but it's only half the story....