Azure Storage Services
All Azure Storage services live inside a storage account, which defines the billing, redundancy, and access settings shared by all services in that account.
| Storage Service | Type | Best for |
|---|---|---|
| Azure Blob Storage | Object storage | Unstructured data: images, videos, backups, log files |
| Azure Files | Managed file shares (SMB/NFS) | Lift-and-shift file shares, replacing on-prem file servers |
| Azure Queue Storage | Message queue | Decoupling app components, async task processing |
| Azure Table Storage | NoSQL key-value store | Schemaless structured data, IoT telemetry, user data |
| Azure Disk Storage | Block storage (managed disks) | OS and data disks for Azure VMs |
Azure Blob StorageObject storage optimized for storing massive amounts of unstructured data. Blobs are organized into containers (like folders, but flat). Three blob types: Block blobs (text/binary, most common), Append blobs (optimized for appending, e.g., logs), and Page blobs (random-access, used for VM disks). is the most commonly used storage service — unstructured data like images, videos, and logs are stored in containers and accessed via HTTP/HTTPS.
Blob Access Tiers
Blob access tiersStorage tiers that optimize cost vs. access frequency for blob data. The four tiers are Hot, Cool, Cold, and Archive — from highest access cost / lowest storage cost (Hot) to lowest access cost / highest storage cost (Archive). let you optimize cost by matching the pricing model to how often data is accessed:
| Tier | Access frequency | Storage cost | Access cost | Minimum storage duration |
|---|---|---|---|---|
| Hot | Frequent | Highest | Lowest | None |
| Cool | Infrequent (30+ days) | Lower | Higher | 30 days |
| Cold | Rare (90+ days) | Lower still | Higher still | 90 days |
| Archive | Very rare (180+ days) | Lowest | Highest | 180 days |
Archive tier blobs are offline — you must rehydrate (move to Hot or Cool) before you can read them. Rehydration can take up to 15 hours for standard priority.
Storage Redundancy Options
Azure always stores at least 3 copies of your data. The redundancy option controls where those copies are stored:
| Option | Copies | Protection | Notes |
|---|---|---|---|
| LRS (Locally Redundant Storage) | 3 copies within one datacenter | Rack/server failure | Cheapest; no zone or region protection |
| ZRS (Zone-Redundant Storage) | 3 copies across 3 AZs in one region | Datacenter failure | Recommended for HA within a region |
| GRS (Geo-Redundant Storage) | 3 LRS copies primary + 3 LRS in paired region | Regional disaster | Secondary is read-only unless failover occurs |
| GZRS (Geo-Zone-Redundant Storage) | 3 ZRS copies primary + 3 LRS in paired region | Zone + regional disaster | Best durability (16 nines) |
RA-GRS and RA-GZRS are read-access variants that allow reading from the secondary region without failover — enabling higher read availability during a primary region outage.
Storage Account Types
| Account type | Supported services | Supported redundancy |
|---|---|---|
| Standard general-purpose v2 (StorageV2) | Blob, File, Queue, Table, Disk | LRS, ZRS, GRS, GZRS |
| Premium block blobs (BlockBlobStorage) | Block blobs, Append blobs | LRS, ZRS |
| Premium file shares (FileStorage) | Azure Files | LRS, ZRS |
| Premium page blobs (StorageV2 premium) | Page blobs (VM disks) | LRS |
Standard general-purpose v2 is the recommended account type for most scenarios.
Storage Tools and Migration Services
For scripted data transfer, AzCopyA command-line utility for copying data to and from Azure Storage (Blob, Files). Supports copying blobs between storage accounts, uploading/downloading local files, authentication via SAS tokens or Microsoft Entra ID, and synchronization. is the CLI tool of choice, supporting SAS token and Entra ID authentication. For visual management of storage accounts, Azure Storage ExplorerA standalone GUI desktop application (Windows, macOS, Linux) for browsing and managing storage account contents — blobs, files, queues, and tables. Connects using connection strings, SAS tokens, or Microsoft Entra ID. provides a cross-platform desktop GUI. To sync on-premises Windows file shares with Azure Files, Azure File SyncReplicates on-premises Windows file server shares to Azure Files. Enables cloud tiering (infrequently accessed files move to Azure; a stub remains locally), multi-site sync, and disaster recovery. enables cloud tiering and multi-site synchronization. For server and workload migrations, Azure MigrateA hub service for discovering, assessing, and migrating on-premises servers, databases, web apps, and virtual desktops to Azure. Includes discovery and assessment, server migration, and integration with third-party tools. provides the full discovery, assessment, and migration workflow. When internet transfer is impractical due to data volume or bandwidth, Azure Data BoxA physical appliance Microsoft ships for offline data transfer when network transfer is impractical (slow link, large data volume, regulatory requirements). You copy data to the device, ship it back, and Microsoft uploads it to Azure Storage. ships a physical appliance that you fill with data and return to Microsoft for upload.
| Product | Capacity | Use case |
|---|---|---|
| Data Box Disk | Up to 35 TB | Small migrations via USB/SATA SSDs |
| Data Box | Up to 80 TB | Standard large migrations |
| Data Box Heavy | Up to 1 PB | Massive data migrations |
| Data Box Gateway | Virtual appliance | Continuous online data ingestion |
Redundancy Options — Full Comparison Matrix
| Option | Primary Region | Secondary Region | Secondary Readable? | Durability | Best for |
|---|---|---|---|---|---|
| LRS | 3 copies, 1 datacenter | None | N/A | 11 nines | Dev/test, non-critical |
| ZRS | 3 copies, 3 AZs | None | N/A | 12 nines | HA within a region |
| GRS | LRS (1 DC) | LRS (paired region) | Only after failover | 16 nines | Regional DR |
| GZRS | ZRS (3 AZs) | LRS (paired region) | Only after failover | 16 nines | Zone + regional DR |
| RA-GRS | LRS (1 DC) | LRS (paired region) | Always | 16 nines | GRS + always-on read |
| RA-GZRS | ZRS (3 AZs) | LRS (paired region) | Always | 16 nines | Best overall durability + reads |
Blob Access Tier — Cost Trade-off Visualization
Storage Cost: HOT ───────────────────────── ARCHIVE (cheapest storage)
Access Cost: HOT ───────────────────────── ARCHIVE (most expensive to read)
Lifecycle management policies can automatically move blobs between tiers based on last-accessed or last-modified dates — e.g., move to Cool after 30 days, Archive after 180 days.
Migration Tool Selection Guide
| Scenario | Right Tool | Why |
|---|---|---|
| Copy files from on-prem to Azure Blob (scripted) | AzCopy | CLI, supports large volumes, SAS auth |
| Browse and download blobs visually | Azure Storage Explorer | GUI, no CLI knowledge needed |
| Sync Windows file server shares to Azure Files | Azure File Sync | Ongoing sync with cloud tiering |
| Assess and migrate on-prem VMs to Azure | Azure Migrate | Discovery, sizing, migration replication |
| Transfer 500 TB when bandwidth is limited | Azure Data Box | Physical offline transfer; impractical online |
Storage Tier Minimum Retention Penalties
If a blob in Cool, Cold, or Archive tier is deleted or moved before its minimum retention period, you are charged a prorated early deletion fee:
| Tier | Minimum retention | Early deletion penalty |
|---|---|---|
| Cool | 30 days | Charged for remaining days |
| Cold | 90 days | Charged for remaining days |
| Archive | 180 days | Charged for remaining days |
| Hot | None | No penalty |
Explore Azure Storage in the Portal
Step 1 — Create a Storage Account (or browse existing)
- Sign in to portal.azure.com.
- Navigate to Storage accounts → + Create.
- On the Redundancy tab, cycle through the options (LRS, ZRS, GRS, GZRS) and observe how the diagram changes.
- Note that ZRS requires a region that supports Availability Zones.
- Cancel without creating (to avoid charges).
Step 2 — Explore Blob Access Tiers
- Open an existing storage account → Containers.
- Upload a small test file to a container.
- Click on the blob → Change tier → observe the available tiers (Hot, Cool, Cold, Archive).
- Note the warning that Archive tier blobs require rehydration before they can be read.
Step 3 — View Azure Migrate Hub
- Search for Azure Migrate in the portal.
- Open Azure Migrate → Servers, databases and web apps.
- Observe the tools available: Discovery and assessment, Migration and modernization.
- Note that Azure Migrate integrates with third-party tools via its ecosystem.
Step 4 — Explore AzCopy (awareness)
- Navigate to learn.microsoft.com/azure/storage/common/storage-use-azcopy-v10.
- Review the basic syntax for copying blobs between accounts:
azcopy copy 'https://<source>.blob.core.windows.net/...' 'https://<dest>.blob.core.windows.net/...'
AZ-900 Exam Focus
Exam Trap
"Archive tier blobs can be read immediately" — False. Archive tier blobs are offline and must be rehydrated (moved to Hot or Cool tier) before reading. Rehydration can take up to 15 hours for standard priority. This is one of the most tested storage facts on AZ-900.
Exam Trap
"GRS makes the secondary region available for reads at all times" — False. With plain GRS, the secondary is read-only only after a failover. To enable always-on read access to the secondary, use RA-GRS.
Exam Trap
"LRS stores copies across multiple datacenters" — False. LRS stores 3 copies within a single datacenter. No zone or region protection. It is the cheapest option but also the least resilient.
Exam Trap
"ZRS replicates data to a paired region" — False. ZRS replicates within a single region across 3 availability zones. Only GRS and GZRS replicate to a secondary (paired) region.
Exam Tip
Data Box = large offline transfer. Whenever a question involves hundreds of TB, a slow internet connection, or offline transfer, Data Box (or Data Box Heavy) is the answer. AzCopy is for online transfer; Storage Explorer is for GUI browsing.
Must Memorize
LRS = 1 DC, 3 copies, cheapest
ZRS = 3 AZs, 3 copies, no secondary region
GRS = LRS primary + LRS secondary (paired region), no secondary read without failover
GZRS = ZRS primary + LRS secondary (paired region), highest durability
RA-GRS / RA-GZRS = same as GRS/GZRS but secondary always readable
Question — click to flip
Q: What must you do before reading a blob in Archive tier?
Question — click to flip
Q: Which storage redundancy option provides the highest durability (16 nines) while keeping data zone-redundant in the primary region?
Question — click to flip
Q: What is the difference between GRS and RA-GRS?
Question — click to flip
Q: Which Azure tool is used for offline bulk data transfer when internet bandwidth is insufficient?
Question — click to flip
Q: What is the difference between Azure Files and Azure Blob Storage?
Question — click to flip
Q: How many copies of data does Azure always maintain, and what does the redundancy option control?