Submitted by Pixel Chimp on Wed, 18/04/2012 - 13:22

Note to self…

Deploying multiple Macs over 802.11.n isn’t really practical.

Using a 1.27GB Deploy Studio netboot set to boot one Macbook Air took 2:30’s to get to the DS runtime to be able to select a workflow.

A test with 6 machines booting in parallel took 11 minutes for 5 of them to get to the same usable state. One machine failed to boot the netboot set & it sat the at the grey Apple screen, so it probably wasn’t pulling in the netboot image over wifi.

These times don’t include running any restore workflows, so actual restoring could take hours for a large master image. Wifi doesn’t support multicast streams so each client needs to maintain a single connection to the server.


It looks like the wifi speed to each client is around 10MB/s. This is well below the theoretical 300Mbits/s (or 35MB/s) that 802.11.n claims. It is probably closer to 100Mbits/s. This is on a large multi access point network that is common in education environments, e.g. too large for one system admin to kick off all the 802.11.g/b users that may be reducing the network speed. When we tested on a dedicated 802.11.n network (with no b/g clients) it wasn’t much faster.

1 Mac: 1.27GB / 150s = 0.00846 GB/s

or 8.66MB/s

6 Macs*: 7.62GB / 660s = 0.01154 GB/s

or 11.82MB/s

The server showed a peak of around 16MB/s during the netboot period.

*****assuming the 6th Mac did download the netboot image but didn’t boot.

The figures are in GigaBytes & MegaBytes per second since this is the way I find it easiest to think about data transfer for deployment.

Deployment alternatives

The Macbook Air is a beautiful machine, fast & very portable, but the lack of Gigabit ethernet makes them impractical to do mass setup quickly (and conveniently).

The Macbook Air USB to ethernet adapter maxes out at 100Base-T speeds so that is an equally slow option (expect about 4-6MB/s).

Imaging when booted from a USB hard drive (20-25MB/s) could work, but they are also slow compared to Gigabit ethernet (50-60MB/s). You may be able to use a lot of fast USB pen drives if your deployment image is small enough.

The solution

Fortunately Apple are not idiots, they installed Thunderbolt on these machines, so it can be used to quickly clone an image onto a machine. It is quick but there is no clear way to run it on many machines at the same time.

We decided to deploy using a custom installation on one Macbook Air containing the image to deploy. We booted the target Mac in target disk mode & connected via Thunderbolt. It meant that an 8GB compressed image (around 16GB when installed) would take 3:00’s to restore. This equates to 8GB / 150s = 0.0444 GB/s or 45.51MB/s this is about the same speed as Gigabit ethernet. Verification of the restored Mac is included in this time so the transfer is actually quicker (more like 2:30s), but not close to the theoretical 1.25GB/s that is claimed for Thunderbolt.

At £40 per Thunderbolt cable & the ability to only do one machine at a time it seems like a lousy replacement for Gigabit ethernet. Using ‘asr’ to restore from a .command script makes it almost a one click process (once authenticated), it’s not so bad when you boot one to target mode whist the another is imaging, and another is rebooting to complete it’s post imaging tasks. Make the script eject the new machine when done & you can simply unplug & move to the next machine when it’s restored. 3 people did 100 Macbook Airs in about 4-5 hours, I suspect one person could do 100 machines in a day if they had a helper to speed up the unboxing & moving machines around.

All of this could be easier if Apple still made the white Macbook (with a Gigabit ethernet port), but now the Air is seen as the entry level Mac more & more large installations will include Macbook Air’s.

Not including ethernet in these machines is pretty silly. The only reason I can see for not including it is that it would increase the case dimensions around the port. It’s akin to removing ones testicles to improve the fit of a suit.

NOTE: The speeds mentioned for comparison are taken from - List of device bit rates, your actual data rates will vary.


Trying to reimage MacBook Airs

Submitted by Anonymous on Sun, 19/08/2012 - 13:46.

I’m trying to reimage and press Command N upon chime and this doesn’t work with the Thunderbolt/ethernet adaptor.

Previous image worked on white MacBook. Any suggestions?

Use the boot picker instead?

Submitted by Pixel Chimp on Sun, 19/08/2012 - 14:24.

See if holding alt at startup brings up the netboot disk as a boot option.

If that works you know your netboot server is running correctly & the netboot set is setup.

Also check the Startup disk preferences when the Mac is normally booted, it should have the option to select your netboot set if everything is working.

P.S. Just hold N at boot, the command button isn’t needed.