


The last point is important, because the experience very well be much slower than what you’re used to. Patience for a (likely) slower experience.OS X Yosemite Dev Preview downloaded and ready to go.An external drive (USB thumb drive, hard drive, SD card, any external disk) with 16GB of space available or greater (the base OS X 10.10 installation uses about 10GB, and you’ll want some extra space for swap, caches, and test files).Requirements for Installing Yosemite onto an External Disk

You can speed test your external drives with free third party tools if you’re not sure if the performance is particularly good or bad, but it’s safe to say that faster read and write speeds is better. If you’re going to try this, aim to use the fastest possible external drive for the best experience, otherwise you’ll find the entire process and overall OS X 10.10 experience to be quite slow running off an external disk. The method described in this tutorial works to install a bootable OS X Yosemite instance onto any external disk, whether it’s a USB flash drive, a generic external hard drive, or whatever other external volume you have.
