Last week Microsoft released a public preview of a new service called Azure Archive Blob Storage, offering customers a lower-cost cloud storage solution for rarely accessed data. This allows for storage tiering, where organizations can place their critical data on expensive, high-performance storage and then move it down the line as it winds up being accessed less frequently over time.
Last year Microsoft introduced Azure Cool Blob storage, which cost customers a penny per GB per month in some Azure regions. Now, users have another, lower-cost option in Azure Archive Blob Storage, along with new Blob-Level Tiering data lifecycle management capabilities. So there are now three Azure blog storage tiers: Hot, Cool, and Archive (see Azure Blob storage: Hot, cool, and archive storage tiers).
Azure Archive Blob Storage costs 0.18 cents per GB per month when the service is delivered through its cloud data center in the East US 2 (for comparison, in the same region hot is 1.8 cents and cool is 1.0 cents per GB per month) . Customers can expect a 99 percent availability SLA (service level agreement) when the service makes its way out of the preview stage.
Complementing the new service is a new Blob-level Tiering feature that will allow customers to change the access tier of blob storage objects among Hot, Cool or Archive. Also in preview, it enables users to match costs to usage patterns without moving data between accounts.
Archive storage has the lowest storage cost and highest data retrieval costs compared to hot and cool storage.
While a blob is in archive storage, it cannot be read, copied, overwritten, or modified. Nor can you take snapshots of a blob in archive storage. However, you may use existing operations to delete, list, get blob properties/metadata, or change the tier of your blob. To read data in archive storage, you must first change the tier of the blob to hot or cool. This process is known as rehydration and can take up to 15 hours to complete for blobs less than 50 GB. Additional time required for larger blobs varies with the blob throughput limit.
During rehydration, you may check the “archive status” blob property to confirm if the tier has changed. The status reads “rehydrate-pending-to-hot” or “rehydrate-pending-to-cool” depending on the destination tier. Upon completion, the “archive status” blob property is removed, and the “access tier” blob property reflects the hot or cool tier.
Example usage scenarios for the archive storage tier include:
- Long-term backup, archival, and disaster recovery datasets
- Original (raw) data that must be preserved, even after it has been processed into final usable form. (For example, Raw media files after transcoding into other formats)
- Compliance and archival data that needs to be stored for a long time and is hardly ever accessed. (For example, Security camera footage, old X-Rays/MRIs for healthcare organizations, audio recordings, and transcripts of customer calls for financial services)