Thecus N5550 NAS Server Reviewed

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Scott DeLeeuw

NAS Server
At a glance
Product Thecus NAS Server (N5550) [Website]
Summary Aggressively-priced D2550 Atom-based five-drive high-performance BYOD NAS with USB 3.0, HDMI & audio I/O ports.
Pros • Multiple volume support
• USB 3.0 port
• HDMI & VGA ports
• Audio I/O ports
Cons • No WebDAV support
• Very basic IPv6 support
• Only one USB 3.0 port on front panel, covered by door


Thecus recently upgraded its five-bay NAS line with a model based on the Intel D2550 "Cedarview" Atom platform. Today I’m taking a look at the five bay N5550, which looks very much like the N5500 we reviewed back in 2009.

From the front with the door closed, the N5550 and N5500 look almost identical, with just a simple change to the logo. Inside the drive door you’ll find the power switch, reset button and USB 3.0 port (the N5500 has a USB 2.0 port here). The main port changes are on the rear panel, where audio connections have been added, as well as an HDMI port.

You might notice that the USB 3.0 port is only available under the front cover and not on the rear of the unit. This makes for very inconvenient access if you plan to attach a backup drive.

N5550 Front and rear panel callouts

Figure 1: N5550 Front and rear panel callouts

On a more positive note, the N5550 is designed for easy servicing. Removing three thumbscrews and two VGA connector fasteners lets you pull off the back panel and detach the single fan connector to completely free the back panel. The cover then lifts off to completely expose the board.

The N5550 is the first NAS we’ve seen that makes it easy to replace both the main board and drive backplanes. The backplane is held in position via pins on the drive bay frame and secured via standoffs on the back panel.


On the photo below of the N5550’s main board, we can see the 2 GB DDR3 SoDIMM, as well as the heatsinks that cover the 1.86 GHz Intel Atom D2550 processor and companion device. You can’t see it in the photo, but the SoDIMM socket is two-level and there is an empty slot hidden behind the factory-installed RAM. Thecus says you can expand memory to a total of 4 GB.

The part marked “Industrial MDS module” is a 1 GB flash Disk on Memory (DOM). Just to the right of the DOM is what looks to be a mini-PCIe slot. Like the N4800 reviewed back in May, there also appears to be a PCI-e X1 connector to the left of the DOM even though the N5550 spec doesn’t mention an expansion slot either.

N5550 board

Figure 2: Thecus N5550 board

Table 1 summarizes all the N5550’s key components. The design shares a few things with the much higher-end TopTower N6850 reviewed a few months back, including dual Intel WG82574L Ethernet controllers, Silicon Image SiI3132 providing the fifth internal SATA and one external eSATA ports and NEC D720200AF for the USB 3.0 port.

CPU Intel Atom D2550 @ 1.86 GHz
Flash 1 GB DOM
Ethernet Intel WG82574L (x2)
Companion Intel NM10 Express Chipset [guess]
USB 3.0 NEC D720200AF
Audio Realtek ALC262 2+2 HD Audio Codec
SATA Silicon Image SiI3132 SATALink PCI Express to 2-Port Serial ATA II Host Controller
I/O ITE8728F Super I/O
Video Chrontel CH7318 HDMI level shifter
Table 1: Key component summary and comparison

We didn’t remove the heatsink to identify the D2550 Atom’s companion device and couldn’t find any clues in the system’s boot messages. But the Atom D2000/N2000 datasheet shows an Intel NM10 Express Chipset in the block diagram, so that’s our best guess.

The NAS came diskless and was equipped for testing with four Western Digitial Red 3 TB WD30EFRX drives on loan from WD. Power consumption measured 39 W with the 4 drives spun up and 26 W with them down via the programmable idle drive power save feature. Fan and drive noise could be classified as medium-low, since a low whirr could be heard in a quiet home office.


The N5550 was upgraded to 2.03.04.atom firmware before testing. Since Thecus standardizes its feature set across its products we won’t be covering the features here. But a quick look at the N4800 review will provide a good overview. Additionally you could give the online demo a try to really get a feel for the user interface.


The N5550 was tested with 2.03.04.atom firmware using our standard NAS test process.

The Benchmark summary (Figure 3) shows pretty consistent Windows File Copy performance for RAID 0, 5 and 10 modes. RAID 0 write shows the highest results at 106 MB/s, with 97 and 98 MB/s for RAID 5 and 10, respectively. File Copy read is even more consistent at 93, 91 and 95 MB/s for RAID 0, 5 and 10, respectively.

Thecus N5550 Benchmark Summary

Figure 3: Thecus N5550 Benchmark Summary

NASPT File copy results are higher than their Windows File Copy counterparts for write (126, 119, 117 MB/s) , but lower for read (88, 86, 84 MB/s) for RAID 0, 5 and 10m respectively.

iSCSI target write performance to target created on a RAID 5 volume came in at 85 MB/s, with read lower at a still-respectable 80 MB/s.

Thecus’ USB / eSATA Schedule Backup module was used to run backup tests with our new higher-performance Startech USB 3.0 eSATA to SATA Hard Drive Docking Station (SATDOCKU3SEF) containing a WD Velociraptor WD3000HLFS 300 GB drive.

Since Thecus doesn’t provide a way to format external drives, we were only able to test only FAT and NTFS backup formats. Best backup throughput of 45 MB/s was obtained with FAT format and USB 3.0 connection. NTFS backup shared the slowest throughput of 22 MB/s in all three connections (USB, USB 3.0 and eSATA).

Rsync backup to the NAS Testbed running DeltaCopy acting as an rsync target came in at 37 MB/s.

For a competitive look, I ran RAID 5 File Copy charts filtered for dual-core Atom processors. Note that RAID 5 (and 10) tests are run with four drives so as not to give an unfair advantage/disadvantage to NASes with more than four bays.

As we have seen previously, the latest-generation dual-core Atoms (D2700, D2550) don’t seem to provide a significant performance boost over previous generation D525 Atoms. The write comparison in Figure 4 shows the N5550 having comparable performance to the D525 1.8 GHz Atom-based QNAP TS-459 Pro +. The other similarly-performing NASes (Synology DS2411+ and Thecus N4800) use the dual-core 1.8 GHz D525 Atom and dual-core 2.13 GHz D2700 Atom, respectively.

Thecus N5550 RAID 5 File Copy Write Comparison

Figure 4: Thecus N5550 RAID 5 File Copy Write Comparison

RAID 5 File Copy Read falls just a bit, with the N5550 as much as 10% lower than some other dual-core Atom NASes, but still turning in respectable numbers.

Thecus N5550 RAID 5 File Copy Read Comparison

Figure 5: Thecus N5550 RAID 5 File Copy Read Comparison


The Thecus N5550 is one of the most economical five-bay dual-core Atom-based NASes out there, for as low as $550 from reputable etailers. For that price, you’ll be able to copy large files to and from it just about as fast as a Gigabit Ethernet connection will allow.

The N5550 is even cheaper than its four-bay N4800 sibling, although it doesn’t have the N4800’s built-in battery backup. But depending on your needs, you might find a live spare for your RAID 5 array a more useful feature.

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