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The TS-x51A runs the latest version of QNAP's operating system - QTS 4.2.2. We did an in-depth review of QTS 4.1 about the same time as the original TS-x51 models were reviewed. QNAP provides a good overview of the features of QTS 4.2. QNAP's site also provides a link to a 124-page brochure that details all of the features of QTS 4.2.2.

QTS 4.2 features an improved user interface. Below are a couple of screenshots that show the landing page, the control panel and the resource monitor.

QNAP QTS 4.2.2 landing page

QNAP QTS 4.2.2 landing page

QNAP provides a live demo, so you can connect to a demo server and explore features (read-only) yourself.

QNAP QTS 4.2.2 Control panel (l) and Resource monitor (r)

QNAP QTS 4.2.2 Control panel (l) and Resource monitor (r)

Other new features include USB QuickAccess, hardware-assisted AES encryption, and real-time 4K and 1080p transcoding.


QTS 4.2.2 Build 20160812 firmware was loaded onto a TS-451A-4G and performance tests were run using the Revision 5 NAS test process. Since the TS-251A-4G uses the same processor, RAM and Ethernet components, all testing was done on the TS-451A-4G. The TS-451A-4G tests used four drives configured in single RAID 0, 5 and 10 volumes. The TS-251A-4G tests used two drives in single RAID 0 and 1 volumes. All tests were run using Western Digital Red 1 TB (WD10EFRX) drives (x2 / x4 SNB supplied).

Power consumption with four drives was 27 W with all drives spun up, dropping to 13 W with all spun down. Spin up / down consumption for two drives was 16 W and 10 W, respectively. Noise level with both two and four drives was low, with a bit more drive noise with four drives. The fan was virtually silent, even during testing.

The composite image below shows how the TS-251A-4G and the TS-451A-4G compare to other products for File Copy Write Performance. The File Copy Write test for the two-bay test TS-251A-4G was 100.4 MB/s and the TS-451A-4G turned in 102.6 MB/s.

Note that quite a few NASes at the top of both charts are clustered around 110 MB/s. That's about the maximum throughput that you can achieve with single client Gigabit Ethernet testing. For ranking purposes, we consider performance within 5% as equal. However, both of the QNAP TS-x25-4G tests results were outside of the 5% threshold, so this would be an initial indication that write performance could lower the overall Total NAS ranking score.

QNAP TS-251A and TS-451A file copy write performance comparison

QNAP TS-251A and TS-451A file copy write performance comparison

Performance - Two Bay

For the two drive comparison, I chose the original QNAP TS-251 (an obvious choice) and the ASUSTOR AS6102T. The ASUSTOR AS6102T has a similar Intel Braswell N3050 Celeron dual core processor that also supports hardware assisted 256 bit AES Encryption as well as 4K video. And, as of publication, the ASUSTOR was priced $2 less.

The benchmark summaries below show all three NASes. File copy write and read performance was above 100 MB/s for both RAID 0 and RAID 1 for all products except for the 94.3 MB/s File Copy Read performance turned in by the TS-251. Interestingly, the TS-251A-4G's File Copy performance slightly trailed the TS-251's performance except for File Copy Read.

For USB 3 Backup (all formats), the TS-251A-4G held a significant edge over the AS6102T and slightly edged out its TS-251 sibling except for EXT format where it tied at 91.1 MB/s. For network backup, the TS-251A-4G trailed both of the other two NASes but had similar results compared to the TS-251. For the iSCSI Write test, both of the QNAP NASes outperformed the ASUSTOR. For the iSCSI Read tests, the TS-251A-4G had the lowest score of the three products compared.

Benchmark summary comparison

Benchmark summary comparison

The NAS Ranker, filtered for RAID 1 and Revision 5 testing and sorted by ascending price shows that the QNAP TS-251A-4G ranked #10. Looking at the chart, you can see that there are five NASes that were cheaper than the TS-251A-4G, but had better Total NAS rankings. (#6 ASUSTOR AS6102, #2 Synology DS216+, #8 NETGEAR RN202, #4 Synology DS216 and #9 QNAP TS-251).

TOTAL NAS Rank for RAID1 test method Revision 5 NASes

TOTAL NAS Rank for RAID1 test method Revision 5 NASes

The chart below shows the individual and category scores for the same three NASes used in the 2 drive benchmark summaries above. The QNAP TS-251A-4G earned a #10 ranking. It didn't win in any category as compared to the other two NASes. Its best performance was a tie for #4 in the Video category. It did hold a slight edge over its TS-251 sibling for both the Write and Read benchmarks.

Ranker Performance Summary comparison

Ranker Performance Summary comparison

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