Azure Storage Services, Tiers & Redundancy: AZ-900

Azure storage services are the managed cloud services Microsoft Azure provides for keeping data safely and making it available to your applications. Instead of buying and looking after your own disk arrays and file servers, you store data in Azure, and Microsoft handles the underlying hardware, patching, and durability for you. Azure keeps multiple copies of your data so that a single hardware failure does not lose it.

Different kinds of data need different kinds of storage, so Azure offers several distinct services rather than one. Some data is unstructured — photos, videos, documents, and backups that do not fit neatly into rows and columns. Some is a traditional file share that many people or servers open at once. Some is a stream of messages passed between parts of an application, and some is simple structured data such as a lookup table. Azure has a service tuned for each of these.

For the AZ-900 exam you are not asked to configure storage; you are asked to recognize which service fits a described need. Keep the plain-language purpose of each service in mind — object data, file shares, messaging, key-value records, and virtual machine disks — and most storage questions become straightforward matching exercises. The rest of this lesson gives you those purposes, then the two settings you tune on top of them: access tiers and redundancy.

Azure Storage groups several data services under a single account. Here are the ones the exam expects you to tell apart, with the job each one does best.

Azure Blob Storage holds unstructured object data — any file with no fixed format, such as images, video, logs, and backups. Azure Files offers fully managed file shares you mount over the SMB or NFS protocols, so servers and users open them like a network drive. Azure Queue Storage stores large numbers of messages so different parts of an application can communicate without being connected at the same instant. Azure Table Storage is a simple NoSQL key-value store for large amounts of structured but non-relational data. Azure Disk Storage provides the disks attached to Azure virtual machines, acting like a hard drive for a VM.

If a question describes object storage for unstructured data, the answer is Blob; a shared network drive points to Files; a VM's hard drive is Disk Storage.

Azure Blob Storage is Azure's service for object storage, which means storing data as individual objects — each file plus its metadata — rather than in a file-system folder tree or database table. The word blob stands for "binary large object," and it can be anything: a photo, a video, a PDF, an application installer, a log file, or a database backup. This is why Blob Storage is described as being for unstructured data — the service does not care what is inside the object.

Blobs live inside containers, which act like folders that group related objects within a storage account. Each blob has its own web address, so applications, websites, and users can read or write objects directly over the internet using standard requests. That makes Blob Storage a natural fit for serving images and video to a website, holding backups and archives, storing large data sets for analysis, and keeping files that many applications need to reach.

Because it is built for massive scale and pay-as-you-go pricing, you can store a few files or many petabytes and pay only for what you keep and access. For example, a photo-sharing app might store every uploaded picture as a blob and serve it straight from Azure. On the exam, remember the trigger: object storage for unstructured data means Azure Blob Storage, and blobs are the data type whose access tier you choose next.

Not all data is used the same way: some is read constantly, some rarely. Azure Blob Storage lets you pick an access tier so you pay less to store data you seldom touch, in exchange for paying more (and sometimes waiting) when you do read it. There are four tiers to know.

The hot tier is for data accessed frequently: it has the highest storage cost but the lowest access cost, ideal for files in active use. The cool tier is for data accessed infrequently and stored for at least about 30 days — lower storage cost, higher access cost. The cold tier goes further, for data accessed even more rarely and kept for a longer minimum, with cheaper storage still and higher access charges. The archive tier is for data rarely accessed and stored long term, such as compliance records; it is the cheapest to store but is offline, so retrieving data takes time (a retrieval latency of hours) before you can read it.

Exam trigger: rarely accessed, cheapest, with a retrieval delay is the archive tier.

Redundancy means Azure automatically keeps multiple copies of your data so a failure does not lose it. When you create a storage account you choose a redundancy option, and the exam tests which one protects against which kind of failure. The four options build on each other.

Locally redundant storage (LRS) keeps three copies within a single datacenter in one region — the cheapest option, protecting against disk and server failures but not against the whole datacenter going down. Zone-redundant storage (ZRS) copies data across three availability zones in the same region, so it survives one zone (one datacenter) failing. Geo-redundant storage (GRS) keeps copies in your primary region and replicates to a paired secondary region hundreds of miles away, protecting against a full regional outage. Geo-zone-redundant storage (GZRS) combines the two: zone redundancy in the primary region plus geo-replication to a secondary region, the highest durability.

Exam trigger: to protect against a full region outage, choose a geo-redundant option — GRS (or GZRS). LRS and ZRS stay within one region.

Every one of the services above lives inside a storage account — the top-level container that gives your data a unique name and namespace in Azure, and where you set options such as region, redundancy, and performance. You can think of the storage account as the "box" and Blobs, Files, Queues, and Tables as the kinds of data you keep in it. Because the account is where redundancy is chosen, that setting applies to the data inside it.

Azure offers a few account types so you can match cost and performance to your workload. The standard general-purpose v2 account is the common default and supports blobs, files, queues, and tables together with the standard access tiers. A premium account uses solid-state disks for higher performance and lower latency, and comes in variants specialized for block blobs, file shares, or page blobs (the disks behind virtual machines).

Performance is often summarized as two levels: standard, backed by regular magnetic drives and priced for general use, and premium, backed by SSDs for workloads that need consistently fast, low-latency access. For the AZ-900 exam you do not need to memorize every variant — just recognize that a storage account holds your data, that its type and performance level affect cost and speed, and that you pick standard for typical needs and premium when performance matters most.

Once you know where data will live, you need a way to get it there. Azure provides several tools for moving files into and out of storage, and the exam expects you to recognize their names and purposes rather than use them.

AzCopy is a command-line tool for copying data to and from Azure Blob and File storage quickly and in bulk — ideal for scripts and large transfers. Azure Storage Explorer is a free graphical desktop app that lets you browse, upload, and download blobs, files, queues, and tables by pointing and clicking, which suits people who prefer a visual tool. Azure File Sync keeps an on-premises Windows file server in sync with an Azure Files share, so your local server acts as a fast cache while a full copy lives in the cloud.

For larger, one-time moves, Azure offers migration tools. Azure Migrate is a central hub for assessing and migrating servers, databases, and applications into Azure. Azure Data Box is a physical, ruggedized appliance Microsoft ships to you; you copy terabytes of data onto it and mail it back, which is far faster than uploading over a slow internet link when the data set is huge.

For example, a company moving 200 TB of archives with limited bandwidth would order an Azure Data Box rather than upload for weeks, then use AzCopy for smaller ongoing transfers.