FileVault Defaults to on in Mac OS X El Capitan Upgrade Installer
/Just a reminder to Mac users. When upgrading to El Capitan, the installer defaults to turning on FileVault encryption on your hard drive even if your drive wasn't encrypted before. Please make sure to uncheck it if you want to keep your drive unencrypted.
To see if your drive is encrypted or not, go to System Preferences -> Security & Privacy and click on the FileVault tab. As you can see below, my drive is NOT encrypted.
Our recommendation is that you encrypt your drive only if you are very sure you have excellent backups in more than one location because if your drive fails, at least 93% of the sectors will need to be recovered in order to be able to access your data.