It uses commodity hardware. Also, Spanner doesn't really need the atomic clocks, they just help performance. CockroachDB, which is similar, runs fine on commodity hardware.
I seem to have misunderstood Spanner by and large. I thought their achilles heel was the atomic clock since it is this clock which makes consensus at scale possible and there by transactions. Cockroach and Yugabyte both work on similar principles but they use these hybrid logical clocks. The hybrid logical clock is a function of NTP and a monotonic local clock so I guess this works ok for Raft consensus.
From Jepsen - "yugabyte seems mostly resilient to clock skews' - this is a very safe but at the same time a vague statement. What does mostly mean ? Good for 99% of practical use cases ?
I think it means "we can't prove that it works, but we have tested it and we haven't found a case where it doesn't." There are conceivable cases where the hybrid logical clock won't work, but most of these are cases where other systems will fail first (eg TLS/SSL).
Edit: To address the first part of your comment, the atomic clocks narrow the bounds on how bad your NTP clock can be. Spanner essentially waits out the bounds on clock variance on each write transaction to get consistency. There still would be a measurable bound on your clock precision without the atomic clock, but it would be a lot larger.
