To help us provide you with free impartial advice, we may earn a commission if you buy through links on our site. Learn more

QNAP TS-251 review

Our Rating :
Price when reviewed : £410
inc VAT

The QNAP TS-251 is a powerful NAS with many media and business features


Capacity: N/A, 3.5″ hard disk bays (free): 2 (2), Networking: 2x 10/100/1000 Ethernet, DLNA media server: Yes, Print server: Yes, Dimensions (WXHXD): 102x169x225mm, Weight: 1.28kg

DEAL ALERT: You can currently get a QNAP TS-251+ NAS Solution with 4TB of storage, which is a very similar model to the one reviewed below, for £303 on Amazon. That’s a massive reduction from the RRP, which is £462. To claim that deal, you just have to click here.

Michael’s original review continues below.

The QNAP TS-251 is a powerful NAS with a vast array of features, such as on-the-fly media transcoding and the ability to run multiple virtual machines (VMs) in addition to the usual file sharing and backup services we expect from all NAS devices. 

These technical feats are made possible by a dual-core, 2.4GHz Intel Celeron processor, which is a very powerful chip by NAS standards. Our unit only came with 1GB of RAM, though, and you’ll need more RAM if you want to run multiple virtual machines. A 4GB version (TS-251-4G, £327 from is available for very little more than the machine tested here, and both devices can handle up to 8GB of RAM.

As the TS-251 is an enclosure, you’ll need to buy your own disks to use with it. Initial setup is simple, and although the installation of hard disks requires screws, these are supplied in the box. The NAS is made of high-quality material and doesn’t feel like it’ll fall apart easily.

There’s a USB3 port on the front for high-speed file transfers from external disks, with a further three USB ports on the rear, including one USB3 connector. There’s also dual gigabit Ethernet ports for extra performance and redundancy.

Once switched on and fully updated, the TS-251 presents you with the QNAP QTS operating system. It’s similar to the interfaces used by Synology and Asustor, and looks like a Linux desktop system. At times, QTS feels slow, particularly when the NAS is undertaking multiple jobs, such as media transcoding or file transfers, but most of the time it’s responsive.

QTS can be little confusing at first glance, with menus and submenus often obscuring some of the more basic functions. Luckily, the Control Panel app has a search box to help you find the specific feature you’re looking for, meaning you don’t have to spend too much time hunting through menus. Setting up file shares, users and backups is very straightforward. There are also more advanced features preinstalled such as a MySQL server, a VPN service and a web server.

The App Center has plenty of additional pieces of software available to download, and it’s about as well-stocked as Synology’s Package Station. There are also various mobile applications for both iOS and Android devices, and these are among the best we’ve seen. They have clean interfaces and, unlike many NAS partner apps, they’re fairly stable.

^ The QNAP TS-251 lets you keep an eye on the videos currently being transcoded

Media transcoding is a function available with both the Synology DS214play and the DS415play. Both of these devices impressed us because they were able to keep up with media transcoding of 720p videos, which is an important feature if you’re streaming video to devices such as a smart TV or a PC running Windows Media Player.

You can also have files in specific folders be transcoded as soon as they’re transferred to your NAS. This means that real-time transcoding isn’t required, but you will end up with multiple versions of the same file on your NAS; if you haven’t invested in high-capacity hard disks, this may be a problem. You can choose to have them transcoded to 240p, 360p, 480p, 720p and 1080p. This worked without a hitch: 20-minute TV shows were transcoded in about 15 minutes and looked great on our Samsung Smart TV.

On-the-fly transcoding is equally seamless.  Typically, Samsung TVs can’t play MKV files, but when we selected our test MKV video, it started instantly and played in high quality. You can keep an eye on which files are currently being transcoded in the Transcode Management part of the operating system.

Aside from the media and virtualisation functions, the NAS also has an HDMI output. Like comparable models from Asustor, such as the AS-202TE, this lets you run media centre programs such as XBMC directly from your NAS, using it like a living room media PC.

File transfer performance is good, although perhaps not as fast as we’d expect from a NAS at this price. Large files were written at 84.2MB/s and were read at 103.82MB/s. Smaller files were written at 23.8MB/s and read at 9.5MB/s. This is slightly below the speeds we saw with the cheaper but equally business-ready Synology DS214+, although that device didn’t have on-the-fly multimedia transcoding abilities or VM features.

In order to run virtual machines, you’ll need at least 4GB of smaller, SO-DIMM memory. Because the NAS only ships with 1GB, you’ll need to disassemble it in order to fit your own. This isn’t a simple process and requires the removal of four screws on the back of the NAS and then a further set of internal screws. You then remove internal chassis that holds the hard disks in place, which is far too involved for our liking. It seems strange to advertise the virtual machine feature on a NAS which doesn’t come with the necessary hardware to do this out of the box. As mentioned, you can buy a 4GB version of the TS-251 for a similar price.

The QNAP TS-251 is a good NAS with a vast array of features and powerful hardware, and it can do a lot at once. The TS-251 is expensive, though, and if your needs are more modest but you still want a relatively powerful NAS, you should consider the Synology DS214+ or the Asustor AS-202TE, as both are much cheaper.

Default file systemEXT4
File attribute supportYes
Price per gigabyteN/A
Hard disk interfaceSATA3
3.5″ hard disk bays (free)2 (2)
Networking2x 10/100/1000 Ethernet
Front USB ports1x USB3
Rear USB ports2x USB2, 1xUSB3
Other portsNone
Universal Plug and PlayYes
DLNA media serverYes
Print serverYes
USB disk serverYes
Web serverYes
FTP serverYes
Mac file sharingYes
Other servicesMobile apps, camera server, app store
Dimensions (WXHXD)102x169x225mm
Buying information
WarrantyTwo-year RTB
Part codeTS-251

Read more