AZ-900 Azure Storage Services Guide

Azure Storage Account Types

Azure storage begins with a storage account, which acts as a unique namespace for all your storage data accessible over HTTP or HTTPS. For the AZ-900 exam, you need to understand the two primary account types: Standard general-purpose v2 (GPv2) and Premium. GPv2 accounts support Blob, File, Queue, and Table storage and are backed by magnetic drives (HDD). Premium accounts use solid-state drives (SSD) and are optimized for low-latency scenarios.

A storage account name must be globally unique across all of Azure, between 3 and 24 characters, and can only contain lowercase letters and numbers. This uniqueness requirement is because the storage account name becomes part of the endpoint URL — for example, https://mystorageaccount.blob.core.windows.net. Understanding this structure helps you answer questions about how Azure identifies and routes storage requests.

Storage accounts also determine which redundancy options are available to you. Not all redundancy configurations are available for all account types or regions, which is an important nuance for the exam. For a broader view of how storage fits into the Azure ecosystem, see our cloud concepts guide and our dedicated networking guide for how virtual networks interact with storage endpoints.

Azure Blob Storage

Blob (Binary Large Object) storage is Azure's solution for storing massive amounts of unstructured data — things like images, videos, documents, backups, and log files. Blobs are organized into containers within a storage account, and each blob can be up to 190.7 TB in size. There are three blob types you must know for the AZ-900 exam:

• Block blobs — optimized for uploading large amounts of data. Text and binary files, media files, backups. Most common type.
• Append blobs — optimized for append operations. Ideal for logging scenarios where data is continuously added.
• Page blobs — optimized for random read/write operations. Used as the backing store for Azure Virtual Machine disks.

Blob storage supports three access tiers — hot, cool, and archive — which control how data is stored and how much it costs to access. This tiering system is one of the most tested topics in the storage domain. We cover tiers in detail in the access tiers section below.

Azure Files

Azure Files provides fully managed file shares in the cloud, accessible via the industry-standard Server Message Block (SMB) protocol and the Network File System (NFS) protocol. Unlike Blob storage which uses a flat namespace, Azure Files uses a hierarchical file system — making it a drop-in replacement for on-premises file servers.

Key use cases for Azure Files include lift-and-shift migrations of applications that rely on file shares, shared configuration files across multiple virtual machines, and diagnostic data like logs and crash dumps. Azure File Sync can extend Azure Files into on-premises environments by caching frequently accessed files locally while storing everything in Azure. For tips on passing the exam, see our AZ-900 pass guide.

Queue Storage and Table Storage

Azure Queue Storage provides reliable messaging for asynchronous communication between application components. Messages can be up to 64 KB in size, and a queue can contain millions of messages. Queue storage decouples components so they can scale independently — for example, a web front-end adds work items to a queue, and a background worker processes them at its own pace.

Azure Table Storage is a NoSQL key-attribute store for semi-structured data. It stores data as collections of entities, each with up to 252 custom properties. Table storage is cost-effective and well-suited for storing flexible datasets like user data for web applications, address books, or device information for IoT scenarios. For the AZ-900 exam, know that Table storage is part of Cosmos DB's table API offering as well.

Azure Storage Redundancy Options

Redundancy is among the most frequently tested storage topics on the AZ-900 exam. Azure automatically stores multiple copies of your data to protect against hardware failures, network outages, and natural disasters. You choose the redundancy option when you create your storage account, and it determines how and where your data is replicated.

There are four redundancy configurations to know:

• Locally Redundant Storage (LRS) — replicates your data 3 times within a single datacenter in the primary region. Lowest cost. Protects against drive and rack failures but not datacenter-level outages.
• Zone-Redundant Storage (ZRS) — replicates your data synchronously across 3 Azure availability zones in the primary region. Protects against zone-level failures. Good for high availability within a region.
• Geo-Redundant Storage (GRS) — replicates data 3 times in the primary region (like LRS) and asynchronously replicates to a secondary region hundreds of miles away. Protects against regional disasters. Data in secondary is not readable unless Microsoft initiates a failover.
• Geo-Zone-Redundant Storage (GZRS) — combines ZRS in the primary region with asynchronous geo-replication to a secondary region. Highest durability. Designed for critical data needing both zone and regional redundancy.

A key exam distinction: GRS and GZRS also have read-access variants (RA-GRS and RA-GZRS) that allow you to read from the secondary region endpoint at any time — not just during a failover. The secondary endpoint URL has a -secondary suffix appended to the account name.

Blob Storage Access Tiers

Azure Blob storage offers three access tiers that let you balance storage costs against access costs. The AZ-900 exam expects you to know the trade-off for each tier:

• Hot tier — optimized for data accessed frequently. Highest storage cost, lowest access cost. Default tier for new storage accounts.
• Cool tier — optimized for data infrequently accessed and stored for at least 30 days. Lower storage cost than hot, but higher access cost. Suitable for short-term backups and disaster recovery.
• Archive tier — lowest storage cost, but data is stored offline. Takes hours to rehydrate (move to hot or cool) before you can read it. Intended for data that can tolerate several hours of retrieval latency — long-term backups, regulatory archives.

Tiers can be set at the blob level (not the account level), so you can have hot and cool blobs coexisting in the same container. Lifecycle management policies can automatically move blobs between tiers based on rules you define — for example, moving blobs to cool after 30 days and to archive after 90 days.

Azure Managed Disk Types

Azure Virtual Machines use managed disks as their block-level storage volumes. Managed disks are backed by Azure Storage and are fully managed by Azure — you don't have to manage storage accounts for them. There are four disk types:

• Ultra Disk — highest performance, configurable IOPS and throughput. For SAP HANA, top-tier databases, and transaction-intensive workloads.
• Premium SSD — high performance SSD-backed. For production workloads and performance-sensitive applications.
• Standard SSD — cost-effective SSD option. For web servers, lightly used enterprise applications, dev/test.
• Standard HDD — lowest cost, magnetic drives. For backup, non-critical workloads, infrequent access.

For the AZ-900 exam, you are not expected to memorize IOPS figures, but you should know the general positioning: Ultra Disk is top-tier, Premium SSD is production-grade, Standard SSD balances cost and performance, and Standard HDD is lowest cost for non-critical use.