Storage Tiering service processing

The Storage Tiering service processes one object at a time. For each object, the service checks the applicable service plan to determine the storage tiers on which copies of the object data should be stored, the number of copies of the object data that should be stored on each tier, and the number of copies of the object metadata that should be stored on primary running storage. The Storage Tiering service then checks to see whether the object data has been read from a storage tier for which rehydration is enabled. Finally, the Storage Tiering service checks to see whether the object data has been read from a remote system because that object is metadata-only on the local system, and if so, the service checks to see whether rehydration is enabled for the metadata-only tier on which the object resides.

For each object in a namespace, if all of these conditions are true, the storage plan takes no action on that object:

  • The object is stored on the correct storage tier.
  • The correct number of copies of the object data exist on the current storage tier.
  • The correct number of copies of the object metadata exist on primary running storage.
  • If the object is on a storage tier for which rehydration is enabled, the correct number of rehydrated copies of the object exist on the ingest tier.

If one or more of the above conditions is not true, the Storage Tiering service takes the applicable actions to bring the object into compliance with the namespace service plan.