Why macbook wifi file transfer so slow?
August 1, 2013 4:04 PM   Subscribe

Copying files between a macbook and a macbook pro over wifi is slow. Why?

I'm transferring largish (100MB) files between a 2008 white macbook (4,1) with osx 10.7.5 and a macbook pro (mid 2010) also with osx 10.7.5.
Both machine are connected to a home network router (an Asus RT-N56U with the latest firmware) and show that they are both connected with 802.11n (as shown when option-clicking the menu wifi icon), but I only ever see 3 or 4 MB/sec when transferring. How come i can not reach the much higher speeds that 802.11n promises? What can I do to improve transfer speeds?

posted by SueDenim to Computers & Internet (10 answers total)
When I did this I just plugged a ethernet cable into each laptop and they are able to form a mini 2 machine network you can share files between.
posted by Captain_Science at 4:22 PM on August 1, 2013

Air rate bandwidth on an 802.11n AP is "shared", so if you're doing a file transfer from one laptop to another you may see only 4MB/s, while a unidirectional file copy from wireless to a wired laptop might achieve 7-8MB/s. Is the AP in question 2x2 MIMO? That will have a significant effect on throughput. Also I am not sure if the 2008 plastic macbook has a 1x1 or 2x2 antenna in it. If it is 1x1 (802.11n MCS7 best case link 64QAM modulation) your speeds will be much slower than if it can make use of a 2x2 AP.
posted by thewalrus at 4:54 PM on August 1, 2013 [1 favorite]

the 4,1 macbook just doesn't have spectacular wifi. I've hit this exact same bottleneck on an identical machine i used to own. It says it's wireless N, but that's almost a bit deceptive. it's the very earliest generation that just wasn't awesome.

The 2010 macbooks have OK, but only 2x2 wireless N. The bottleneck here is the older macbook, and also just that wireless totally sucks for this. For these types of files i just like using an external hard drive(not a flash drive). With a proper one i've gotten 50-80mb/s after it gets rolling, or roughly 10 second file copies for files this size.

The cable suggestion is also a good one.

It's going this slow because wifi sucks at this kind of thing. ALL wifi is "half duplex", meaning it's either sending or receiving. It doesn't matter if it's a really nice router(which yours is, honestly) or even if every machine involved is 3x3.

This kind of thing sucks even with brand new machines with fixed, large diversity antennas connecting to a really high end commercial AP at my work. We played around with it for a while, and ran in to a bunch of people who went "Hmm, yea that should be faster shouldn't it" and eventually i just ran cables.

So yea, you improve transfer speeds by using a different networking method, or sneakernetting the files. Both of those machines have Gigabit ethernet, which would probably let you saturate the (not amazing 5400rpm, but still) hard drive speeds of both machines. It'll likely be faster than anything you plug in to the USB ports.
posted by emptythought at 6:23 PM on August 1, 2013

1. Data rates are measured in both megabits per second (Mbps) and megabytes per second (MBps), so even a 150Mbps connection will only transfer 15 megabytes/s. And that's assuming you are inside a radio isolation chamber.

2. Cut that in half because you have PC-router and router-PC, so you're left with 7.5 MBs. (The good news is that if you plug in even one of the machines to the router by Ethernet, you'll double the rate.)

I have a 2012 Retina MacBook Pro talking to a 2012 Mac Mini via a 2013 Airport Extreme (so pretty much the best conditions short of 802.11ac, because they each have an extra antenna) and I'm seeing only 6MBs sustained.
posted by wnissen at 9:42 PM on August 1, 2013

If I were in your situation, I'd carry one of the laptops to the other one, boot one in target mode (hold down the T key during boot until the Firewire symbol comes up), connect a firewire cable type that they both share and Bob's your uncle at a couple of hundred MB/second.

If there's ever another option, I'll choose it over wifi when doing anything like file transferring.
posted by Sphinx at 11:58 PM on August 1, 2013 [1 favorite]

Have you tried using AirDrop? With AirDrop, the computers connect directly to each other rather than through the existing Wi-Fi network.
posted by archagon at 2:35 AM on August 2, 2013

Copying files between a macbook and a macbook pro over wifi is slow. Why?

Because wifi sucks. Use a cable.
posted by flabdablet at 10:49 AM on August 2, 2013 [1 favorite]

In addition to the issues people have already mentioned, 802.11n drops off quickly with distance. When I'm in the same room as my router, diagnostics on the laptop and router report 250-300Mbps. Put a wall or two in the way and it can fall off by 2-4 fold. Also, laptop hard disks aren't exactly speedy.

For what it is worth, right now my laptop is reporting a 270Mbps transmit and the router is reporting a similar speed to my laptop. Transferring a 250MB file from a NAS wired directly to the router to the SSD on my laptop, I get ~15-20MB/s, but the first time I transferred it, it was more like 7, because, I'd guess, it hadn't been cached on the NAS. So, your speeds aren't terrible for WiFi, but you could probably do better with a wired connection.
posted by Good Brain at 1:41 PM on August 2, 2013

Have you considered an ethernet cable? Recent Macs (not sure about 2008, but I think they do this too) autosense crossover, so you don't need a special crossover cable - just turn off WiFi on both and hook them up to each other with a regular ethernet cable. They should show each other's hard drives under the Shared heading. You'll get much faster transfers than WiFi.
posted by RedOrGreen at 2:36 PM on August 2, 2013

Response by poster: Looks like an Ethernet cable is probably the only solution that will work for me. Thanks to all who answered.
posted by SueDenim at 4:07 AM on August 4, 2013

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