Torus implements a kind of MVCC, yes. As for read-many-to-write-one, I assume you're talking about Reed-Solomon or similar erasure coding? There have been some papers written about ways to reduce that, a good one is from Facebook: https://code.facebook.com/posts/536638663113101/saving-capac.... And that's just one option. Also, this is all speculative since we have yet to implement erasure coding.
If only one host at a time has access to a given virtual block device, there are some opportunities to buffer outgoing writes with a write-through cache. That might be the way to go if you explore erasure coding in the future.
Well, good luck with it. Don't get me wrong, I'd love 1.5x redundancy overhead instead of 3x. But even if you have to downgrade to offering either replication or XOR, it's still a huge missing piece of the typical container deployment, so good luck.
