USB3 or SATA3 port for external disk?

I have u7621-06 that has USB3 and SATA3 ports. I want to use the router as basic file server.
However when I use USB3 port, I barely get 40 mbyte/s transfer speed via Ksmbd.
It's said that CPU is the bottleneck. Does Sata3 use less cpu than USB3?
(I can't test this myself because current kernel for my router doesn't support ASM1062 SATA Controller)

test speed ssd or hardisk ?
filesystem into unit


mips 1004Kc at 2*880 isn't that fast and samba is quite CPU intensive.

Compared to USB2, USB3 has less of a CPU overhead. While SATA is likely to be slightly better, I wouldn't expect much of a difference compared to USB3. You will need something better than mt7621a for significant performance improvements.


What would you suggest less CPU intensive alternative to Samba?
Anything else?

At the risk of speaking for slh, he is suggesting more CPU, not less CPU usage.

Even the most bare bones dedicated economy NAS will have more than two to three times the CPU capability of a MT7621: ARMv8 running at ~1.4 GHz, Intel Celeron, etc. There are some routers that approach this, e.g., WRT3200ACM, but the u7621-06 with MT7621 SoC is not one of them. While it is running your basic server, your router CPU also has to route your network traffic.

You may get some improvement using Ksmbd, but your router CPU is going to limit performance. That is just fine if all you want is a backup disk or a disk to occasionally (and slowly) share files. I did that for a year or two myself, but it did not take long before I migrated to a 2 bay NAS.

It is more expense, but if you want a performant basic file server, I recommend a dedicated 2 bay NAS. As you start using the file server more, it will not be long before you start thinking about fault tolerance (RAID), backup strategy and various other things a dedicated NAS will just handle better.


Vendor mentioned "Samba accelerator" in the product description.

I asked them about it and here's their unhelpful response: "Hi, It is relative with your firmware setting under Openwrt. You can check on the INTERNET."

Do you have any idea what that is?

This sounds like the capabilities of the MediaTek CPU. The next sentence goes on to describe that.

OpenWrt supports hardware NAT for MT7621. The option appears in the LuCI firewall menu after selecting the software flow offloading checkbox. That may take routing load off your CPU and free up CPU a bit.

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These are read speeds I got
ksmbd: 35-40 mbyte/s
samba4 with Enable extra Tuning+Force synchronous I/O enabled: 80-100 mbyte/s

I'll stay with samba4 for a while.

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