USB 3.0 external HDD attached to WLAN router (vs NAS)

With routers now having USB 3.0 ports and decent processors, I'm wondering how speedy a USB 3.0 external HDD attached to a wireless router would function for file transfers, compared to a NAS. Consider the following setup; which of the following would be the limiting factor when it comes to speeds?

• External HDD rpm? (5400rpm? 7200rpm? I'm not sure what speeds the WD MyBook external HDDs are, anyway)
• USB 3.0 speeds?
• Linksys EA8300 WLAN router quad-core 716mhz processor?
• 867mbps 5ghz (2x2) wireless AC?

And how would the above setup compare to a gigabit ethernet-attached NAS? Surely the processor in a NAS would be better than the router, which would take the load off the router, but for simple file storage, maybe it is is sufficient if you don't need some of the advanced features of a NAS? And if the speed is limited by the wireless AC, rather than the router's internal processor, then it doesn't make sense to invest in a NAS if it won't improve speeds over wireless.

I'd just be interested in seeing a real-world comparison of the the two scenarios (NAS vs USB 3.0-attached external hard drive) without having to buy both setups and testing...

 

Still not great. The router in question EA8300 is powered by a Qualcomm IPQ4019 SoC.

Smallnetbuilder runs a storage performance test on devices they test so finding devices that use Qualcomm IPQ4019 SoC among the ones they tested gives you an answer:

So far 15.7 MB/s write and 30 MB/s read (NTFS) [ SOURCE]

Using smallnetbuilder again:

write throughput chart for USB 3.0 driver formatted in NTFS - here
As you can see - two first ones are really doing good (100MB/s), next two are decent (70 MB/s), the fifth one is acceptable (55MB/s) and the rest are plain slow.

For read (NTFS, USB 3) is looks a bit better - here
First 4 contenders look very good (100-ish MB/s) and subsequent two are looking good (80-90 MB/s) however since you need both parameters to be decent you'd be lookib at two routers that are rather good at it.

 

Wow, thanks. So from this (if I'm reading this correctly) it seems that it's the router's processor that is the limiting factor. That surprises me, because I didn't think that read/write to a hard drive would be that intensive on the router's processor, unlike streaming or encoding or something. I guess I should buy a decent NAS, or else I will have to spend a lot of money on a very powerful router in order to get decent speeds on the HDD...

Edit: Wait, is the "15.7 MB/s write and 30 MB/s read" numbers from a gigabit ethernet NAS... or a USB 3.0-connected drive? I'm confused, because that seems low for a NAS.

 

From a USB drive.

It's not really just the read/write - it's mostly NTSF. These are Linux based and if it was EXT4 that would probably look a lot better.