In theory, if you raise it properly, a dog will never attack a guinea pig. But sometimes, a dog has a bad temper, and she can do it. It depends on the breed very much. As far as I know, the kindest and calmest dogs in the world are Labradors, and it seems to me that my Labrador will never hurt anyone in his life. Of course, if that's the case, I deserve a bit of praise, too, -- I regularly read articles about the
happiness of dogs [cleverpuppies.com] and what needs to be done for your dog to grow happy and be calm. Therefore, think about such a breed as a Labrador or an Akita Inu. So good luck to you ;)