The Asustor Nimbustor 4 Gen2 AS5404T is something of a mixed bag. In fairness to Asustor, it's by now an older device and the use of DDR4 memory in the minus category above is simply due to the fact that costs are going up, which could make it an expensive upgrade option down the road, rather than being related to as something that is negatively impacting the performance. Asustor does appear to have a good combination of software and hardware as far as performance goes, as despite using a now four-year-old SoC, its keeping even pace with more modern hardware in the same price range.

The construction of the AS5404T leaves a bit to be desired though, especially when it comes to the M.2 expansion board, which simply can't be fitted with SSDs that have heatsinks, both due to the spacing of the drives and the recurring issue of housings that have limited internal space, regardless of the manufacturer. We do like the clips that hold the NVMe drives in place though. Having a second memory slot for upgrades is great, but having the RTC battery hidden away in such a location that you have to tear apart the entire NAS to get to it is really going to be annoying one day when the battery runs out, even more so because it's almost within reach. We also ran into an issue where the AS5404T simply wouldn't power on properly after having been shut down, but this was a random issue, and we couldn't work out why it was happening. This was frustrating, but normally a NAS is running 24/7, which makes this less of a problem, but an issue nonetheless.

It's good to see that Asustor is using a fairly recent Linux kernel, with 6.6.x being deployed with ASM 5.0.1, but we don't really understand why so many NAS manufacturers like to obscure the actual version in use. Asustor has also made sure the HDMI port can be used for something beyond accessing the UEFI, even though its Portal virtual machine solution isn't the best implementation we've seen. What really impressed us with the AS5404T was the SMB multichannel implementation, as it worked flawlessly against our host system with a 10 Gbps card in it and although dual 2.5 Gbps ports doesn't quite reach the full potential of a single 5 Gbps interface, it does provide a significant performance boost in many use cases, while still having some limitations. That said, this is the first time we've seen it working, as enabling it on other NAS appliances we've tested has brought zero improvements.

As for Asustor's OS, ADM feels a tad dated as we've pointed out, it does offer some features that TerraMaster and Ugreen are missing, but it's still not as feature packed as QNAP or Synology's operating systems. ADM does deliver more features than what most people would need and it's not a bad OS as such, it just needs a bit more up-to-date UI/UX. On the other hand, Asustor is by far on the most recent Linux kernel we've seen by any of the NAS makers, which is also a big plus, even though the full version is obfuscated. It does at least show that Asustor has built its OS on a recent platform, unlike say QNAP which is based on what can only be called an ancient kernel for the TS-432X. Another plus in Asustor's hat is the three-year warranty, which is a year longer than its competitors and something that is always welcome.

Performance wise, we have no real complaints about the AS5404T, it delivers as good performance as more modern hardware and even outperforms it—if we compare it to the TerraMaster F4-424—in many of the tests we ran. It's a bit give and take, as it's not a clear winner by any means, at least not until you use it with SMB multichannel, then the competition doesn't stand a chance in the tests that stand to benefit from SMB multichannel. The downside is that not everything benefits from SMB multichannel, but the upside is that no special hardware is needed to benefit from it, at least as long as your PC has a 5 or 10 Gbps network card in it, or a pair of 2.5 Gbps network interfaces.

It's tricky to sum up the Asustor Nimbustor 4 Gen2 AS5404T, as the performance from the older hardware is there, the software is up-to-date under the hood, and with things like SMB multithreading working out of the box, it's a pretty tempting package. However, we can't disregard it being a dated platform, which could be a cause for concern when it comes to upgrades down the road. Then there's the issue with not being able to use heatsinks on the SSDs, besides some other minor things that detract from an otherwise solid piece of kit. If you're looking for a US$500-ish NAS, then it's by no means a bad purchase, as long as you're aware of the limitations, although Asustor is far from the only NAS manufacturer that has peculiar oddities with its products, in this case some of these peculiarities are also what robs it of an award.