If an external volume is to have OS X installed and used as the startup disk, is it a requirement that it be connected directly to a port on the computer, rather than to a port on a hub, such as a USB hub? Where is this documented by Apple?
iMac, OS X El Capitan (10.11), 27" iMac 24 GB memory
Hi bobgoldstein,
Good question whether an external boot drive needs to be connected directly to the computer rather than a hub.
That is mentioned at the bottom of this article.
Starting from an external USB storage device (Intel-based Macs) - Apple Support
Learn more
If you're using an external USB hub with several connected USB devices, the external USB storage device you wish to start from may not be recognized, or, may need to be connected directly into one of the computers USB ports instead. Some computer keyboards that include USB ports may not supply enough power to some external USB hard drives.
Take care.
Thanks for the reference. I just spent two days with long phone calls to AppleCare, struggling with a failure to install and boot from El Capitan on and external SSD drive. Neither of my two Apple 'Advisors' thought to mention this requirement. I finally noticed that my drive was connected with a hub, and when I changed it to a port on my iMac, all was well.
Must an external boot drive be on a port?
