Rehydrate an archived blob to an online tier

To read a blob that is in the Archive tier, you must first rehydrate the blob to an online tier (Hot or Cool) tier. You can rehydrate a blob in one of two ways:

  • By copying it to a new blob in the Hot or Cool tier with the Copy Blob operation. Microsoft recommends this option for most scenarios.
  • By changing its tier from Archive to Hot or Cool with the Set Blob Tier operation.

When you rehydrate a blob, you can specify the priority for the operation to either standard priority or high priority. A standard-priority rehydration operation may take up to 15 hours to complete. A high-priority operation is prioritized over standard-priority requests and may complete in less than one hour for objects under 10 GB in size. You can change the rehydration priority from Standard to High while the operation is pending.

You can configure Azure Event Grid to fire an event when rehydration is complete and run application code in response. To learn how to handle an event that runs an Azure Function when the blob rehydration operation is complete, see Run an Azure Function in response to a blob rehydration event.

For more information about rehydrating a blob, see Blob rehydration from the Archive tier.

Rehydrate a blob with a copy operation

To rehydrate a blob from the Archive tier by copying it to an online tier, use PowerShell, Azure CLI, or one of the Azure Storage client libraries. Keep in mind that when you copy an archived blob to an online tier, the source and destination blobs must have different names.

After the copy operation is complete, the destination blob appears in the Archive tier. The destination blob is then rehydrated to the online tier that you specified in the copy operation. When the destination blob is fully rehydrated, it becomes available in the new online tier.

The following examples show how to copy an archived blob with PowerShell or Azure CLI.

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Rehydrate a blob by changing its tier

To rehydrate a blob by changing its tier from Archive to Hot or Cool, use the Azure portal, PowerShell, or Azure CLI.

To change a blob's tier from Archive to Hot or Cool in the Azure portal, follow these steps:

  1. Locate the blob to rehydrate in the Azure portal.

  2. Select the More button on the right side of the page.

  3. Select Change tier.

  4. Select the target access tier from the Access tier dropdown.

  5. From the Rehydrate priority dropdown, select the desired rehydration priority. Keep in mind that setting the rehydration priority to High typically results in a faster rehydration, but also incurs a greater cost.

    Screenshot showing how to rehydrate a blob from the Archive tier in the Azure portal

  6. Select the Save button.

Bulk rehydrate a set of blobs

To rehydrate a large number of blobs at one time, call the Blob Batch operation to call Set Blob Tier as a bulk operation. For a code example that shows how to perform the batch operation, see AzBulkSetBlobTier.

Check the status of a rehydration operation

While the blob is rehydrating, you can check its status and rehydration priority using the Azure portal, PowerShell, or Azure CLI. The status property may return rehydrate-pending-to-hot or rehydrate-pending-to-cool, depending on the target tier for the rehydration operation. The rehydration priority property returns either Standard or High.

Keep in mind that rehydration of an archived blob may take up to 15 hours, and repeatedly polling the blob's status to determine whether rehydration is complete is inefficient. Using Azure Event Grid to capture the event that fires when rehydration is complete offers better performance and cost optimization. To learn how to run an Azure Function when an event fires on blob rehydration, see Run an Azure Function in response to a blob rehydration event.

To check the status and priority of a pending rehydration operation in the Azure portal, display the Change tier dialog for the blob:

Screenshot showing the rehydration status for a blob in the Azure portal

When the rehydration is complete, you can see in the Azure portal that the fully rehydrated blob now appears in the targeted online tier.

Screenshot showing the rehydrated blob in the Cool tier and the log blob written by the event handler

Change the rehydration priority of a pending operation

While a standard-priority rehydration operation is pending, you can change the rehydration priority setting for a blob from Standard to High to rehydrate that blob more quickly.

Note that the rehydration priority setting cannot be lowered from High to Standard for a pending operation. Also keep in mind that changing the rehydration priority may have a billing impact. For more information, see Blob rehydration from the Archive tier.

Change the rehydration priority for a pending Set Blob Tier operation

To change the rehydration priority while a standard-priority Set Blob Tier operation is pending, use the Azure portal, PowerShell, Azure CLI, or one of the Azure Storage client libraries.

To change the rehydration priority for a pending operation with the Azure portal, follow these steps:

  1. Navigate to the blob for which you want to change the rehydration priority, and select the blob.

  2. Select the Change tier button.

  3. In the Change tier dialog, set the access tier to the target online access tier for the rehydrating blob (Hot or Cool). The Archive status field shows the target online tier.

  4. In the Rehydrate priority dropdown, set the priority to High.

  5. Select Save.

    Screenshot showing how to update the rehydration priority for a rehydrating blob in Azure portal

Change the rehydration priority for a pending Copy Blob operation

When you rehydrate a blob by copying the archived blob to an online tier, Azure Storage immediately creates the destination blob in the Archive tier. The destination blob is then rehydrated to the target tier with the priority specified on the copy operation. For more information on rehydrating an archived blob with a copy operation, see Copy an archived blob to an online tier.

To perform the copy operation from the Archive tier to an online tier with Standard priority, use PowerShell, Azure CLI, or one of the Azure Storage client libraries. For more information, see Rehydrate a blob with a copy operation. Next, to change the rehydration priority from Standard to High for the pending rehydration, call Set Blob Tier on the destination blob and specify the target tier.

After you have initiated the copy operation, you'll see in the Azure portal that both the source and destination blob are in the Archive tier. The destination blob is rehydrating with Standard priority.

Screenshot showing destination blob in Archive tier and rehydrating with Standard priority

To change the rehydration priority for the destination blob, follow these steps:

  1. Select the destination blob.
  2. Select the Change tier button.
  3. In the Change tier dialog, set the access tier to the target online access tier for the rehydrating blob (Hot or Cool). The Archive status field shows the target online tier.
  4. In the Rehydrate priority dropdown, set the priority to High.
  5. Select Save.

The destination blob's properties page now shows that it is rehydrating with High priority.

Screenshot showing destination blob in Archive tier and rehydrating with High priority

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