Swift/erasure-codes/regions

How does erasure coded data work with the concept of regions?

Three options:
 * It doesn't
 * Cross-region replicate the chunks
 * Increase the parity bits for each region

A nice goal would be for a remote region to help participate in rebuilding EC objects if that cannot be done in the local region.

Generally, erasure coding shouldn't be attempted when a low-latency WAN traversal is required (ie regions). All EC data for an object (or enough to rebuild the object) should be stored in a single region.