External Hard Drive(s) -- Linux can run from a traditional USB flash drive. We have tested both Unbuntu and Debian from flash drives. You can get by with a 32GB drive, but we recommend a minimum of 64GB so you have room to add applications and files. For optimal performance, we recommend that you use an external SSD drive instead of a flash drive. The installation will be a bit quicker, boot time will be faster, and performance will be better.
Installation time -- while Linux will install much more quickly than Windows, expect to spend at least an hour creating an external Linux boot drive, especially if you have never done it before.