Got my iMac back from the 3TB Seagate recall warranty service. The repair by an "Apple Authorized Service Provider" was the fodder for another thread of disaster. My goal has been to wipe my new Fusion volume and execute a fresh install of El Capitan. As an aside, the AASP did return the unit with El Capitan, all up to date. Don't ask me why and I'll tell you no lies. Basically, this particular Southern Oregon service provider is horrible and I do not trust their work. We'll leave it at that. So, once I cleaned all of the finger grease smears off of my glass screen and all the hot chocolate sneeze spittle off the back of my iMac; I set it up on my desk and using Carbon Copy Cloner, I cloned my last up-to-date Yosemite image shot immediately prior to taking it in for service on 12/2/2015. I then downloaded "Install OS X El Capitan.app" and used DiskMaker X 5 to create an 8GB USB Flash drive. I then proceed to boot using the option key and select the USB drive "OS X 10.11 Install Disk - 10.11.2", open Disk Utility, highlight Macintosh HD and click "Erase". This results in a Stop sign symbol and error, the process failed. I've ended up with an El Capitan upgrade over the Yosemite. I would still like to solve what I was or wasn't doing wrong that prevented a successful wipe or nuke-n-pave of the "Fusion" drive. This is really the Cliff Notes version of me hammering on the Mount feature, Erase feature, looking for a WTF button, restarting, well, you get the idea. All of the online guides have me wondering what the Hell I'm doing wrong.