When moving an object to a storage tier that includes only economy or extended storage pools, the storage tiering service moves only the object data onto the economy or extended storage that’s used for the new tier. HCP keeps all metadata, including custom metadata, for the object on primary running storage. The system metadata for an object points to each specific NFS volume and each specific economy or extended storage bucket, container, and namespace that’s used to store the data for that object. Primary storage keeps metadata even if economy storage is used as an ingest tier alternative to running storage instead of as a storage tier.
All objects added to a namespace are first written to the ingest tier defined in their namespace service plan. However, HCP can read object data directly from any storage component the object may later be tiered too.
The service plan for a given namespace defines one or more storage tiers for that namespace and specifies a separate DPL setting for each tier, including the ingest tier. When an object is moved from one storage tier to another, all copies of the object data are removed from the previous tier, and the object data is then stored only on the new tier. The DPL setting for the new tier is the total number of copies of the object data that must be stored on that tier, and it’s also the total number of copies of the object data that must be stored in the HCP repository. (For a metadata-only tier, the DPL is zero.)
When the storage tiering service moves an object in a given namespace from a storage tier that includes only ingest tier storage pools to a tier that includes only extended storage pools, the storage tiering service removes all existing copies of the data for that object from the ingest tier storage and stores the specified number of copies of the object data only on the extended storage that’s represented by the pools that are configured for the new storage tier.
The storage tiering service moves all copies of the data for an object to economy or extended storage only if all of these are true:
•The cryptographic hash algorithm for the object has been stored in both the primary and secondary metadata for the object.
•The object is not still open for write. For more information on open objects, see Using a Namespace or Using the Default Namespace.
•The namespace that contains the object has a service plan that defines an storage tier that includes only economy or extended storage pools, and the object meets the criteria for being moved to that tier.
While the data for an object is stored only on economy or extended storage:
•If the object is deleted, the data that’s on the economy or extended storage is also deleted
•If the object is an old version that’s pruned, the version data that’s stored on the economy or extended storage is also deleted
•If the object is shredded, the data that’s stored on the economy or extended storage is not shredded
•New data cannot be appended to the object (assuming the namespace has appendable objects enabled)
For more information on the movement of objects between primary storage and economy or extended storage, see Storage tiering service and Working with service plans.
For more information about economy and extended storage, see Storage for HCP systems.
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