Copy queue prioritization

Each cluster maintains its own list of copies to acquire, then satisfies that list by requesting copies from other clusters in the grid according to queue priority. Prioritization of volumes that are acquired to satisfy the copy queue occurs according to virtual volume copy type in the following order:

1. Immediate
2. Synchronous-deferred
3. Immediate-deferred
4. Deferred

Virtual volume copy types can be more precisely under each of the parent categories listed above. Acquisition of volumes to satisfy copy queue requests will exhaust all volume copy types in one parent category before making a request from another parent copy type. Figure 1 depicts the order in which copy types are acquired to satisfy incoming copy queue requests.