Dell PowerStore Protecting Your Data

Retrieve - additional considerations

When the original source of a backup snapshot that is retrieved from the DD no longer exists (orphan snapshot), blocks on the newly created volume that were not written to when the original volume was backed up, are allocated and written with zeros. As a result, the physical and logical capacities are the same (when looking at the retrieved backup capacity data). When the new volume is mapped to a host, the used and free space are displayed correctly. For details, see Dell Knowledge Base Article 000208504 (After retrieving PowerStore from Data Domain...).
When a source volume or volume group no longer exists on the PowerStore cluster, retrieving the respective backup always results in the creation of a new source together with the retrieved snapshot.
If the size of the retrieved snapshot does not match the size of the source volume, the retrieval is full (the entire snapshot is copied from PowerProtect to PowerStore.
Incremental retrieval (retrieving only the changes that occurred since the backup), occurs if the following conditions are fulfilled:
- The size of the source volume has not changed since it was backed up.
- Both the source volume and the latest remote backup exist on the PowerStore cluster.
The average transfer rate for an incremental retrieval may not always be accurate, although the retrieval progress percentage accurately reflects the amount of retrieved data.