It's interesting to read about Durable Objects. It strikes me as conceptually very similar to what's called Virtual Actors, or Grains specifically in Microsoft Orleans, even if the underlying infrastructure is quite different. Seems like they struggled with naming as well.

One critical thing that I couldn't find info about is what reliability to expect from the persistent storage for a Durable Object. Is it more or less a write to a single disk without redundancy? If there's redundancy, to what degree? Essentially, how much would you need to build on your own in terms of replication for a production scenario if using Durable Objects as primary storage?

I get that they can use other, separate storage if necessary, but either way it seems like an important consideration when designing a system on top of them.