I would like to make my blog highly available. My plan is to install the blog on multiple host, and put a load balancer in front of it. The thing I am worried about is my theming and its static files. From what I understand the theme is installed on the server which receives the request of the theme upload. Is there a way I can upload the theme by accessing the server through SSH. If so would I just have to put it in <ghost_installation_base_path>/content/themes/. or do need to change anything else.
Ghost is highly available all by itself and does not support clustering. If you’re concerned about performance under load then straightforward caching is the answer.
This is sad 
. Load balancing is not just for load aspect but what if for some reason if there is a hardware failure.
Also BTW which cache would you recommend
all things with CND and cache is high available…but not by itself.