In this post, we will learn about Azure Blob rehydration. Azure Storage support three different level of storage tiers Hot storage tier, Cool storage tier, and Archive storage tier. With the different level of storage tiers, you can choose what types of tier needs for your data. We use hot storage tier for those data which are accessed very frequently. Cool tier intended to access less than hot tiers, in general for at least 30 days. Archive tier is intended for long-term data backup or archival purpose and will remain in the tier for at least 180 days. Hot tier has the highest storage cost and lowest access cost, whereas the archive tier has the lowest storage cost and highest access cost. You may read more about these access tier from here.
Chance Access Tier to Archive
In the previous post, we have seen how we can update Access Tier in Azure Storage Blob Level. You can update the tier from Hot or Cool to Archive Tier.
You can easily change the access tier at blob level for storage accounts. If you want to perform this action from Azure Portal, open the respective Azure Blob. Then select the “Blob Properties”. From the properties window, you can change access tier for the blob to Hot, Cool or Archive. Read this post step by step guidance.
Once the Access Tier is moved to Archive tier, your Blob will be inaccessible. Archive storage is offline. At this time if you want to access the blob you will get “This operation is not permitted on an archived blob” error.
Azure Blob Rehydration
To access your archive data back, you need to rehydrate back your storage tier to either Hot or Cool. This process is called Blob Rehydration. The rehydration process may take several hrs. ( up to 15 hrs. to complete) .
When the rehydration is in progress, the blob will be still inaccessible. You can start the rehydration process by just updating the tier for the blobs, and check the status of the rehydration.
Once the rehydration is complete, you can start access the data. This types of access tier ideal Long-term backup, and archival datasets where frequent data access is not required. Archive tier has the lowest storage cost and highest access cost.