What is Block Storage?
October 28, 2025
3 min read
This content is from the lesson "5.2 Block Storage" in our comprehensive course.
View full course: Cloud Fundamentals Study Notes
Block storage is a high-performance storage solution that provides raw, unformatted storage volumes to compute instances (like Virtual Machines).
It's designed for workloads that require low-latency access and high throughput, similar to a traditional hard drive.
Definition:
- Block storage stores data in fixed-size blocks, each with its own unique address.
- These blocks are presented to a server (e.g., a Virtual Machine) as raw, unformatted volumes, which the operating system can then format and use just like a physical hard drive.
- It's often used as the primary storage for operating systems, databases, and applications that require persistent, high-performance disk access.

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How It Works & Core Attributes:
- Structured Data Focus (Often): While it can store any data, it's typically used for structured data that requires frequent read/write operations, such as databases, or for operating system files.
- Direct Attachment: Block storage volumes are "attached" to a single compute instance, similar to plugging a hard drive directly into a computer.
- High Performance: Designed for low-latency and high input/output operations per second (IOPS), making it suitable for demanding applications.
- Persistent Storage: Data stored on block volumes persists independently of the compute instance. If the VM is shut down or terminated, the block storage volume and its data can remain.
- Operating System Control: The operating system within the attached compute instance has full control over the block volume, including formatting it with a file system (e.g., NTFS, ext4).
- Scalable Capacity & Performance: You can typically increase the size and performance (IOPS/throughput) of block volumes independently.
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Analogy: A Dedicated Hard Drive for Your Cloud Computer Imagine you're setting up a new desktop computer.
Your Computer (Virtual Machine): This is your cloud compute instance.
The Hard Drive You Install (Block Storage):
- This is the block storage volume. You buy it, connect it directly to your computer, and then you have to format it (e.g., install Windows or Linux on it, or create a drive for your files) before you can use it.
- It's dedicated to your computer, and you have complete control over its contents and how it's used.
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Common Applications:
- Operating System Boot Volumes: The primary disk where the operating system of a Virtual Machine (VM) is installed.
- Databases: Storing relational databases (like MySQL, PostgreSQL, SQL Server) or NoSQL databases that require high-performance, consistent disk I/O.
- Transactional Applications: Applications that perform many small, frequent read/write operations, such as enterprise resource planning (ERP) systems or customer relationship management (CRM) systems.
- Virtual Desktops: Providing persistent storage for individual user desktops in a virtual desktop infrastructure (VDI) environment.
- Development and Testing Environments: For applications that need dedicated, high-performance disks.
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Quick Note: The "High-Performance Disk"
- Block storage is your "high-performance disk" in the cloud.
- It's the go-to choice for applications that require the performance and behavior of a traditional hard drive directly attached to a server, making it essential for operating systems, databases, and other I/O-intensive workloads.
TAGS
CloudCloud StorageBlock Storage
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