Migrate the entire running stack

A option to migrate the entire stack from existing/running computes hosts to another computes host.

For example,

There are two computes nodes available. Both the compute node have shared storage system.
I have launched a stack (with 6 instances)
In the first compute node, 3 instances are running and in the second compute node 3 instances are running.
Now the first compute node will go to maintaince mode, so there is a need to migrate the 3 instances of
first compute node to secound compute node.

Mannually we can do it from the nova, but there is need to have a option to migrate complete/require instances
of stack to migrate at one time.

Any suggestion or improvements are welcome. Please let me know if you have query's.