Two. Run one in warm/hot standby, optionally with synchronous commits if you want (nearly) guaranteed zero data loss, and can tolerate the increased write latency.
Technically you’ll need a third server to perform the failover, but it doesn’t need to be nearly as big, as it’s just watching heartbeats and issuing commands.
I’m a mid-30-something who has worked in all three as well as several of the “alt cloud” providers. Typically identified as Linode, DigitalOcean, Hetzner, sometimes Rackspace. I’ve used all of those and more.
Bare metal is absolutely where it’s at for base infrastructure and bang-for-you-buck.
People call me a graybeard for such things, but it’s never been said derisively or sarcastically to my face. Usually it’s asking for advice.
I took a “traditional” path here. I started when “the cloud” was just the fluffy white cloud that said “Internet” or “Other Networks” at the top of the diagram.
Technically you’ll need a third server to perform the failover, but it doesn’t need to be nearly as big, as it’s just watching heartbeats and issuing commands.