QNAP TS-251B Review

QNAP TS-251B Review
With the heart of a PC, the QNAP TS-251B can be so much more than a NAS box. Find out why in our full review.

Should I Buy The QNAP TS-251B?

Our Verdict
  • The multi-faceted aspect of the QNAP TS-251B almost succeeds in being something special. Although, it is undoubtedly a better NAS box than a PC, especially if you need media presentations without a Chromecast and you are willing to locate it alongside the TV.

Price When Reviewed

  • $306.99
When the first NAS drives appeared, many of them had video outputs, since it was considered logical that they should be connected to the TV and sit alongside it. However, the noise of whirring fans and the advent of streaming hardware like the WDTV and Chromecast persuaded many NAS makers to do away with video output and concentrate their hardware on network services.

Thankfully some makers, QNAP included, decided to retain a media focused product line which explains the existence of the TS-251B. But, does it offer a combination of NAS and media player that doesn’t compromise either requirement?


QNAP has two versions of the TS-251B. The TS-251B-2G has 2GB of RAM, and the TS-251B-4G comes with 4GB of memory. The UK cost of the smaller memory model is £285.99 and the larger, reviewed here, is £350.99. You can buy it from Amazon, Ebuyer, and Broadband Buyer.

There are specific US versions, the TS-251B-2G-US and TS-251B-4G-US, and these can be found on Newegg for $293.10 and $306.99 respectively and Amazon.

The only significant competition for this device is the Asustor AS6302T, which is also a dual-drive NAS that uses the Celeron. It costs $269 for the 2GB RAM model on Amazon.com, and £269.99 from Amazon.co.uk.

Check out our chart of thebest NAS drives to see what else is available.

Design & Build

Synology might disagree, but QNAP has taken the quality lead in small NAS enclosures to our mind. The TS-251B is a very polished and well-constructed machine that uses a simple metal internal cage with finely injection-molded plastic skin covering it.

A sliding and lockable door on the front opens to reveal the two plastic drive trays that can take either conventional hard drives or SSDs in either the 3.5in or 2.5in form factors.

The drive trays are plastic, and tool-less if you’re installing 3.5in drives. But, making them from anything more substantial would be pointless. Since the majority of owners will install two drives, close the door, and never open it ever again.

On the front face is a single USB 3.0 port, an associated button for dumping USB connected media and a power button. Lights are present for each drive, status, LAN and USB activity, and a power on/off button. It’s all very simple, and even without referring to the documentation, it should be obvious what each button does, and light represents.
QNAP TS-251B Review
The back of the TS-251B is more interesting since it includes several outputs that a typical dual-drive NAS don’t usually sport.

The commonplace items are another four USB ports, one of which is 3.0 spec and others are 2.0, and it has a single Gigabit Ethernet port, and a power inlet for the external laptop-style PSU. The surprise feature is an HDMI 1.4b port that supports output at 4K, but sadly only at 30Hz.

The outside piqued our interest, mostly about what was inside the TS-251B.

Specs & Features

This might seem a rash thing to suggest, but the QNAP TS-251B is a PC.

Please understand, we’re not trying to be clever with the definition of ‘person computer’, at its core this NAS box is powered by an Intel Celeron J3355 dual-core CPU, uses a PC chipset, has DDR3L SO-DIMMs and even a half-height PCIe card slot (PCIe Gen 2 x2).

It wouldn’t be a stretch of the imagination to believe that Windows could run on this platform, given its specification. Instead, here it is running QTS 4.0, a Linux distro created by QNAP designed to deliver NAS functionality with installable apps.

Without a doubt the most potentially useful feature is that PCIe slot, as using cards you can add M.2 storage, 10GbE networking or even a USB 3.1 Gen 2 (10Gbps) Port. What slightly takes the shine off this feature is that this slot is PCIe Gen 2 x2 slot.
QNAP TS-251B Review
The theoretical bandwidth of PCIe Gen 2 is 5GT/s, and two lanes double that to 10GT/s. But those are bits, not bytes, and with various overheads, the fastest that data can travel through this interface is around 800-1000MB/s. That's well below the best that an M.2 NVMe drive or 10GbE networking can deliver, so best curb your expectations if you install either of those options.

A scenario where it might work well enough is one where the TS-251B is used as an overnight backup to another 10GbE connected NAS, as it should be possible to shift more than 3TB per hour even with this architectural bottleneck.

Compared with a typical dual-drive NAS, the computing power in this box is substantially greater, allowing for many more running apps and the hardware transcoding of video files in real-time.

Having not tested a QNAP NAS for a while, we were very pleasantly surprised how the QNAP QTS operating system has developed and the wide range of apps that are now available.

QTS 4.0 & Hardware Transcoding

The selection of apps, the power offered by a dual-core Celeron and the ability to extend the networking to 10Gbe all elevate this design to a unique tier within collective NAS world.

Each time we revisit QNAP we’re more impressed with the QTS operating system, the maturity of it and the now substantial number of apps. QNAP might still be marginally behind Synology in this respect, but the separation has now become paper-thin.
QNAP TS-251B Review
The app selection has tools for developers, media presentation, security camera recording and many others. The selection even includes the LibreOffice suite, that with the attachment of a screen, mouse and keyboard enables the TS-251B to be used almost like a conventional office computer.

For those that are more interested in media storage, Plex Media Server can also be installed to augment the QNAP provided media tools. The subject of Plex brings us neatly to one of the catches in this solution, specifically the playback and transcoding of various video packaging files.

With HDMI output, this NAS should be perfectly positioned for leveraging the hardware decode capability of its processor to deliver smooth video and audio file presentations and QNAP has several homegrown apps facilitate this.

However, a while ago QNAP changed its policy regarding video and audio codecs support for AC3 and DTS audio and its installation of ffmpeg no longer supports the transcoding or presentation of files that use those technologies.

For the very technically minded it is possible to install a statically compiled version of ffmpeg that includes support for AC3 and DTS. But for most users, this isn’t something they’d be able to accomplish or fix again after the next official update obliterates those changes.
QNAP TS-251B Review
The obvious answer is to use Plex as it is licensed to handle these scenarios, but we suspect that on this platform Plex only supports accelerated transcoding up to 1080p, as the processor usage is much higher when presenting 4K content.

If you don’t use any content that was processed using commercial codecs, then it won’t impact you, but for those wanting a front end for a video collection, legal or illegal, this limitation might be a showstopper.

Given how good the hardware is, and the maturity of the QNAP Linux-based QTS, these licensing changes have undermined some of the best aspects of this platform, even if we appreciate the imperative to control licensing costs for QNAP.


The selection of apps, the power offered by a dual-core Intel Celeron and the ability to extend the networking to 10Gbe are all very attractive aspects to the TS-215B.

That you can use this system as a PC with the installable Office applications is cute, even if you could buy a cheap laptop for less that would come with a screen and keyboard for the price.

For those that want a single system that performs all the duties of a NAS box and is also a small computer then this is a perfect choice! But it doesn’t offer the same flexibility as a laptop or small desktop system, should your needs later change.

Where it is excellent is in managing and distributing a media collection, either directly to a TV or via streaming, where it can transcode video and audio tailored for the specific connected device.

It’s just to get the best experience you must also be a Plex Pass subscriber if you want the transcoding of video with AC3 or DTS audio on this hardware.


  • CPU: Intel Celeron J3355 dual-core 2.0GHz processor (boost up to 2.5GHz)
  • GPU: Intel HD Graphics 500
  • Hardware Transcoding: Yes
  • Memory: 4GB SO-DIMM DDR3L (1 x 4GB)
  • Operating System: QTS 4
  • Drives: 2 x 3.5-inch SATA 6Gb/s, 3Gb/s
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About Wanni Arachchige Udara Madusanka Perera

Hey, I'm Perera! I will try to give you technology reviews(mobile,gadgets,smart watch & other technology things), Automobiles, News and entertainment for built up your knowledge.
QNAP TS-251B Review QNAP TS-251B Review Reviewed by Wanni Arachchige Udara Madusanka Perera on February 01, 2021 Rating: 5


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