AirPort Extreme transfer speeds

However, when I access this drive through the AirPort Extreme the speeds are always at 11.2MB/s or less, but usually at this speed.

Mostly it is processor / memory limitation.

And Apple not taking time to optimise the file transfer. Even the Time Capsule will not get USB2 speed 60MB/s. Generally it works around 40MB/s as max speed peaking a bit higher on read. You will find most routers are in this sort of range.

Memory limitation of a router is also part of the problem.. although with better optimisation it would be hugely improved.

It takes a lot of work to tweak some of those values when memory and CPU cycles are in short supply.

Tesserax did some good work measuring speeds to USB disk on Airport and pretty much agrees with your number.. a bit faster read; a bit slower write.

https://discussions.apple.com/docs/DOC-3395

You can see from this why we recommend a real NAS.. it is hugely superior to any router USB.

There are a few routers now that do get close like the Linksys WRT1200AC up series. They can also reach the magical 100MB/s i.e. saturate gigabit. Unfortunately they are not compatible with Time Machine or Apple in general.

Why is it running so much slower

First of all, the USB port on the AirPort Extreme, is USB 2.0......ancient.

Second, the processor inside the AirPort Extreme limits the USB port to a maximum of about half of normal slow USB 2.0 speeds. Typically, speeds are closer to about a third of normal USB 2.0, and often less in my experience.

It's unfortunately hard to find a NAS with equal design

The Time Capsule was the only product on the market that combined a router and a hard drive in the same package. If your requirements call for this type of all-in-one design, then you'll need to look for a new, refurbished or used Time Capsule. Check out Ebay.

The next best option might be a router from Synology or Asus that will allow a USB 3.0 drive to connect and support Time Machine backups. That makes two separate items instead of one, but there are advantages here.....much faster speeds at the USB port and much more advanced router design.

If you already have another router, you don't need two, so all that you need is a NAS.

Synology is what a number of us here use.. It is very well tuned to the Apple environment.

As btw is the Synology router RT2600AC which does a very decent job if you want a cheap solution with a USB drive.

It can achieve the same speed as the Time Capsule and I have got very speedy transfers with them at times.. around 70MB/s although it won't sustain that value if you copy small files.