As with all fault-tolerant NASes, I performed a "drive pull" test on the NAS540. The NAS540 was configured for RAID 5 and had about 70 GB of data copied onto it. I initiated a file copy to add some additional music to the NAS, then unplugged drive 2 during the file copy. While the file copy continued, the LED indicator corresponding to drive 2 turned red. That was the only indication there was a degraded condition; there was no audible alert. Logging into the NAS, there is no indication anything is amiss. You have to navigate to Storage Status to see the Volume marked as being degraded. By looking at the drive list, I could see drive 2 was missing.
I let the file copy continue until it had completed, then re-inserted drive 2. While some NASes automatically start a RAID rebuild, the NAS540 takes a more conservative approach. Through the Storage menu, when a new drive is inserted, a "repair volume" appears. When you click on that option, the next page shows which disk is missing, and which disk is available to repair the volume. I repaired the volume.
RAID rebuild took a bit over three hours to return the volume to "Healthy" status. According to ZyXEL, the length of time required to rebuild (resync) is a function of the size of the disks, and how much data needs to be resynced. I was pleased to see the log file recorded storage related events including the drive failure, replacement and successful rebuild. The short gallery below shows the RAID failure notification and resync sequence.
Performance tests were run using the Revision 5 NAS test process with firmware version V5.04(AATB.0)_20150813. All tests were run using Western Digital Red 1 TB (WD10EFRX) drives ZyXEL supplied with the test sample.
For Benchmark Summary and NAS Ranker performance comparisons, I compared the least expensive NAS, the Thecus N4310 and the next most expensive NAS, the D-Link DNS-340L. The Benchmark Summary shows all test results for each product.
In reviewing the charts below, a few things stand out. First, there aren't NAS540 test results for iSCSI because the product doesn't support iSCSIyet. ZyXEL says iSCSI support is slated for sometime later this year. Second, the ZyXEL NAS significantly outperformed the other two for USB 3.0 backup for FAT, NTFS and EXT3 file formats. In fact, depending on the file format and which other NAS you compare, the ZyXEL had 2-3 times the backup throughput for attached storage.
Network backup, however, was a different story. The NAS540 achieved only 18.4 MB/s compared to Thecus' 42.5 MB/s and D-Link's 33.1 MB/s. If you do a line-by-line comparison of all 33 tests (excluding iSCSI), you'll discover that the ZyXEL had the best score on 24 tests, compared to D-Link's 3 top scores and Thecus's 6 top scores.
Benchmark summary comparison for Zyxel NAS540 (left), D-Link DNS-340L (center) and the Thecus N4310 (right)
Since buyers are usually looking for best bang for the buck, I took our usual approach of sorting the NAS Ranker's results by ascending price. The chart below shows the Thecus and D-Link tied for number 18 (last).
What's important in this chart, however, is that the second least expensive ZyXEL NAS540, priced at $231 at time of review, came in at #15. This means it not only outperforms the Thecus N4310 and D-Link DNS-340L, but also the much more expensive ASUSTOR AS-204TE at $351. To move up a notch in performance to #14, you'd have to spend around $10 more for the ASUSTOR AS-304T.
NAS Ranker filtered for RAID5 showing Total NAS ranking sorted on ascending price
Most of the improvements in performance can directly attributed to faster processors and/or more memory. Both the Thecus and the D-Link NASes use a single core processor. The next most expensive NAS, the ASUSTOR AS-204TE uses an Intel Atom CD5310 and the AS-304T uses an Intel Atom CE5335 - both of which are dual core processors.
Drilling down into the performance of the three NASes allows us to look at individual and category comparisons. The composite chart below shows the detailed performance for the ZyXEL NAS540 (left), D-Link DNS-340L (center) and the Thecus N4310 (right). Of the three compared products, the NAS540 had the best (lowest numbered) ranking in every category.
While the overall ranking for the ZyXEL was #15, on some individual test results, the ranking was up in single digits. For example, for RAID 10 Windows File Copy Read and NASPT RAID 10 File Copy from NAS, the NAS540 ranked #2. Undoubtedly it tied with the more expensive NASes, as the performance was at or near the maximum throughput of a Gigabit Ethernet connection.
Ranker performance comparison for the ZyXEL NAS540 (left), D-Link DNS-340L (center) and the Thecus N4310 (right)
With the NAS540, ZyXEL continues its tradition of offering NASes that offer a lot of features and decent performance at entry level prices. As shown in the NAS Ranker above, to move up to a product with a higher Total NAS ranking, you'd have to spend about 50% more than the NAS540's current $231 price. The chart also shows that it clearly outperformed the cheapest 4-drive NAS (Thecus N4310) and the next two most expensive NASes - the D-Link DNS-340L and ASUSTOR AS-204TE.
But the NAS540 has its weaknesses. It earns our standard criticism given to any "cloud" product that doesn't use a relay server for easy remote access. Relying on port forwarding and especially automatic port opening via UPnP, which many security conscious users disable, for remote access is not user friendly. It also can't handle cascaded NAT networks created by using a router behind ISP-provided modems that usually have their own built-in routers.
Compared to other NASes, the NAS540 also falls somewhat short when it comes to its library of installable apps. QNAP and Synology, for example, have significantly larger libraries of both manufacturer-developed and third party apps available. Finally, ZyXEL needs to do a better job of indicating volume failures and corruption; simply changing the color of a front panel light doesn't cut it.
I like that ZyXEL has been able to successfully integrate music, photo, video and file browsing capabilities into a single app. However, both the iOS and Android versions of the zCloud app lack the capability to automatically back up photos to the NAS540. For that feature, ZyXEL is currently depending on an installable third party app, ownCloud for photo backup. The package is open source and there's a lot of available documentation to wade through. Fortunately, ZyXEL has condensed that into a Knowledge Base article that can help you through setting up myZyXELcloud and using ownCloud. ZyXEL told us their current product road map includes adding photo backup in a future version of zCloud, but with no specific timeline.
With features and performance approaching mid-range NASes, the ZyXEL NAS540 is an excellent choice for buyers on tight budgets looking for a RAID 5 capable NAS.