DP-900 · 3 Describe considerations for working with non-relational data on Azure
Azure Blob storage
Exam objective: Describe features of Azure Blob storage
Azure Blob storage holds unstructured data as blobs inside containers, with access tiers that balance storage cost against retrieval speed.
Azure Blob storage is the Azure service built to hold unstructured data, such as images, documents, logs and backups, as binary large objects called blobs. Blobs live inside containers, and a container is the boundary at which you grant read or write permissions.
There are three blob types. Block blobs suit large files that change rarely, page blobs support random reads and writes, which is how Azure backs virtual machine disks, and append blobs only accept new data at the end, which fits a log file that keeps growing.
| Tier | Best for |
|---|---|
| Hot | Data read or written often |
| Cool | Data accessed rarely, kept at least 30 days |
| Cold | Rarely touched data that still needs a fast read, kept at least 90 days |
| Archive | Data you must keep but almost never read |
Moving a blob to a cooler tier lowers its storage cost but raises the cost, and sometimes the wait, to read it back. Archive can take hours to rehydrate before you can read the blob again. A lifecycle policy can shift a blob through these tiers, or delete it, automatically as it ages.
On the exam, look for containers, blobs, block, page or append, or an access tier name.
Key points
- Blobs live inside containers, and read or write permissions are granted at the container level.
- Block blobs store large binary objects that change rarely, page blobs support random reads and writes such as a virtual machine disk, and append blobs only accept data added at the end.
- The access tier, Hot, Cool, Cold or Archive, trades a lower storage cost for a slower and costlier read later on.
- A lifecycle management policy can move a blob to a cheaper tier, or delete it, automatically as it ages.
- Redundancy options such as locally redundant storage and geo-redundant storage protect blob data against hardware or regional failures.
Exam trap
Archive has the lowest storage cost, but a blob must be moved out of Archive and rehydrated before it can be read, which can take hours. A cooler tier always means a slower, costlier read, not a safer one.
Check yourself
A media company must keep raw video archives it is legally required to retain for years but almost never opens. Minimizing storage cost matters far more than how fast a read comes back. Which blob access tier fits best?
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Checked against Microsoft Learn on October 1, 2026.