It's been a long time since I've done an erase and install and I wanted to ask you guys some questions about it. I'm wanting to erase my Mac completely and reinstall Yosemite, so I have a bootable USB (which seems to take a long time to boot). After booting up I go to disk utility and theres a number of options which is where it gets a little confusing. Previously I've been able to erase DISKS and VOLUMES. Why can I only erase the VOLUME of Macintosh HD? There is the Internal SSD and the USB and there are options below also with yellow icons, can the options below be erased at all? I realise they are for recovery but I thought the system would reinstall these after I erase the disk and reinstall yosemite. Erase and install is not what it used to be on my MacBook Pro, can anyone shed a little light on this because I feel like I'm not erasing everything and I don't like it.