Spacemacs Deletes Irony At Start

[g00sed]

I've installed irony and irony-server several times only to have it deleted when I restart the editor.

[kainarchai]

You should add it to dotspacemacs-additional-packages list or set dotspacemacs-install-packages to used-but-keep-unused in your .spacemacs config file.
It's because spacemacs keeps track of installed packages and removes them if they are not included in specific layer or enabled explicitly.