Maybe you can use one of the data interchange protocols that has a story for backward/forward compatibility? Something like Apache Avro or Protocol Buffers should allow you to work with different versions of your data at the same time.
See: http://martin.kleppmann.com/2012/12/05/schema-evolution-in-a...
His book "Designing Data-Intensive Applications" has a section on this.
If you've scripted the data migration, what besides wait time is the difference between migrating a KB of data and migrating a TB of data?
Maybe you can use one of the data interchange protocols that has a story for backward/forward compatibility? Something like Apache Avro or Protocol Buffers should allow you to work with different versions of your data at the same time.
See: http://martin.kleppmann.com/2012/12/05/schema-evolution-in-a...
His book "Designing Data-Intensive Applications" has a section on this.