How Fast is USB Disk on an AirPort Wireless Base Station?

Warning: This is a technical post, mostly to document and share my experience so others interested might stumble upon it. 🙂

So, I purchased a couple of new 1TB USB hard drives this week and have been trying to figure out how to best set them up for optimal speed and accessibility.  The latest setup is to connect them via USB to my Apple AirPort Extreme Basestation as AirDisks.  I’ll be backing up my laptops to these drives daily (I’ll share the backup details later), so I was curious just how fast I could dump data to them.

How fast should I be able to copy data to the USB hard drive attached to my Airport Extreme?

  • 210 GB/hr (480 Mbps) peak from server – limit of USB 2.0 is lower than my gigabit network
  • 131.8 GB/hr (300 Mbps) peak from laptop – limit of 802.11n

But are those numbers realistic for average write speeds?  I’m currently averaging about 10.5 GB/hr.

Somebody suggested that the Airport Extreme is limited to about 5 MBps (17.57 GB/hr).  This has something to do with the processor in the Airport Extreme (APEB).  Here’s what they’re experiencing:

  • reading from APEB: 16 MBps
  • writing to APEB: 3.5 MBps average and 5-6 MBps peak

3.5 MBps = 12.3 GB/hr which is about what I’m experiencing so far.  I have 4 USB disks connected to by AirPort, but I think this throughput should be for all drives combined.

If you have a USB disk attached to a network with something like the AirPort Extreme, let me know what kind of read and write speeds you are averaging.