How to Rehydrate Azure Archive Blobs to Hot, Cool, or Cold
· 3 min read · Updated
You can't read or modify an Azure blob while it is in Archive. Changing its tier in the portal doesn't make it available straight away: Azure has to rehydrate the data into an online tier first.[1]
There are two methods:
- Change the existing blob's tier with Set Blob Tier.
- Copy the archived blob into a new blob on Hot, Cool, or Cold.
Which one to use depends on retention rules, versions, lifecycle policies, and whether the original archived object must stay untouched.
Standard priority processes requests in the order Azure receives them. Microsoft says objects under 10 GB may take up to 15 hours.
High priority costs more and may complete in under one hour for objects under 10 GB. You can raise an active request from Standard to High, but you cannot lower it again.
Those times are per object. Rehydration throughput is limited for the storage account as a whole, so a large batch can take much longer than the small-object estimate.
Microsoft recommends batching rehydration requests. Progress is easier to watch, and an urgent restore is less likely to become a queue of thousands of objects competing for the account's throughput.
Request the files you need first, and check that they reach the online tier and can be read before you request the rest.
Snapshots and previous blob versions cannot be rehydrated in place. Copy them into a new online blob.
During a recovery, the version you need may not be the current object, so check version and snapshot IDs before you count on Set Blob Tier to bring it back.
Changing an archived blob to an online tier before the Archive minimum duration ends can create an early deletion charge. Copying it into a new online blob leaves the archived source in place and can avoid that fee.
A copy also keeps an existing lifecycle rule from undoing the work. Rehydrating a blob in place does not necessarily reset its last-modified date, so an age-based policy may move it back to Archive. A new copy starts its own object history, which is easier to reason about.
Check current Azure prices before choosing a method. Storage, retrieval, read operations, high-priority rehydration, and early deletion can all affect the bill.[2]
Blober applies a tier change to the Azure blobs you select, so you don't need a PowerShell loop to rehydrate a batch. Azure still controls the rehydration queue and how long it takes.
For a recovery, select a small batch, request the destination tier, and wait for Azure to finish. Then open a few representative files to confirm the data reads, since a changed tier status alone doesn't prove that.
How long does it take to rehydrate an Azure Archive blob? At standard priority, Microsoft says objects under 10 GB may take up to 15 hours. High priority may finish in under an hour for objects under 10 GB. Large batches take longer, because throughput is shared across the storage account.
Can I switch a rehydration request to high priority? Yes, while the request is still active. You can't lower it back to Standard afterwards.
Can I rehydrate a snapshot or a previous version? Not in place. Copy the snapshot or version into a new blob on Hot, Cool, or Cold.
Does rehydrating early cost extra? It can. Moving an archived blob back online before the Archive minimum duration ends can create an early deletion charge, which copying it to a new blob can avoid.