Weird problem with external disks.

[filmbuff]

I'm not sure if this is a problem with Macbook Airs in general or if there is something wrong with mine. Here's the situation: first of all, the USB 3.0 is pretty fast. With any one of my external drives plugged in I can get transfer speeds up to 110 MBps. However, if I have two drives plugged in and I try to transfer from one to the other everything grinds to a halt. The transfer between two external USB 3.0 drives slows to 5MBps. Right now I'm trying to install FSX to an external hard drive in Bootcamp, using an external DVD player on the other USB port. The DVD will spin for 30 seconds then stop for a minute, turn off completely, and finally start back up. The installation is taking forever.

So... what's going on here? I'm using Bootcamp right now and I haven't had a chance to try a large file transer in OSX to see if it makes a difference.

It's worth mentioning that I have one this same operation on my old HP laptop and it worked fine.

 

[dcorban]

I don't know what to say other than I have seen this same phenomenon on my old MacBook. It used to be faster to copy the data from one external disk to the internal disk, then from the internal to the second external. From external to external took forever.

I always assumed it was just an I/O bottleneck due to USB overhead.