PHP POS Redudancy

I'm hosting PHP POS on a third-party web hosting service provider and unfortunately, the web hosting company suffered an outage that crippled my ability to perform any transaction.  I'm familiar with PHP POS having an offline mode but that didn't work at the time.  I don't know how offline mode works, but I assumed it processed off cached memory from the browser.  If someone were to close out the browser, it's a hit or miss trying to get the POS back up and running again.  We frantically tried to load the sales screen and the browser timed out.

I'm wondering if anyone else has this issue and how do you make your POS system more robust?  Can I install a local copy of PHP POS, keep it synced with the cloud version in the background, and only fire it up if the cloud version fails?  This keeps me up at night as my business hangs on by a thread.  It will come to a halt if this happens again.  Any ideas or suggestion is greatly appreciated.