--- title: "What is Block Storage? A comprehensive overview" description: "Discover how block storage works, where organizations use it, and which benefits and requirements matter. Read our article now!" date: 2026-10-05 author: "Denis Arnst" tags: ["Storage"] url: https://www.exoscale.com/blog/what-is-block-storage/ --- # What is Block Storage? A comprehensive overview ![cover](https://www.exoscale.com/blog/what-is-block-storage/cover.png) **Quick summary of this article** - Block storage divides data into individually addressable blocks, enabling precise read and write operations and flexible volume management. - It suits performance-sensitive workloads such as databases, virtual machines, stateful applications, and analytics platforms. - Availability depends on redundancy and coordinated host access, while snapshots and backups determine how effectively you can recover data after failure or corruption. - Block Storage as a Service provides storage capacity on demand while reducing the need to operate the underlying storage infrastructure. - Selecting a block storage solution requires evaluating workload behavior, performance, scalability, resilience, cost, operational controls, and security requirements. Databases and virtual machines require reliable access to persistent storage, often under demanding I/O (input/output) workloads. Cloud migrations and growing data volumes can add further capacity demands. Block storage is commonly used in production environments that require consistent performance, flexible capacity management, and direct access to storage resources. This article explains the definition of block storage, how it works, which types of workloads it supports, and the key criteria organizations should consider when evaluating a block storage solution. ## Definition and Core Concepts of Block Storage Block storage is described as a storage model that divides data into independently addressable units called blocks. Systems can read or modify individual blocks without processing an entire file, while the storage layer itself does not organize data into files and directories. This approach differs from [object storage](https://www.exoscale.com/blog/what-is-object-storage/), where data is stored as self-contained objects together with associated metadata. A volume is a logical collection of blocks that a server recognizes as a storage device. ![block storage vs object storage](https://www.exoscale.com/blog/what-is-block-storage/block-storage-object-storage.png) The operating system can format this volume with a file system and use it for applications or persistent data. The term block-level storage is commonly used as a synonym for block storage and refers to the same underlying storage concept. ## Exoscale Block Storage: Product Overview and Typical Usage Exoscale’s [Block Storage solution](https://www.exoscale.com/block-storage/) provides network-attached block volumes for Exoscale [Compute Instances](https://www.exoscale.com/compute/). The service uses a distributed, redundant architecture that separates persistent storage from instance-local storage. Key characteristics include: * **NVMe-based storage:** Volumes use Non-Volatile Memory Express (NVMe) storage for latency-sensitive, high-performance workloads, offering 5,000 read / 5,000 write IOPS per volume and up to 200 MiB/s. * **Volume specifications:** Sizes range from 1 GiB to 10 TiB per volume, a maximum of 5 volumes can be attached per instance (minimum instance size: Small). * **Availability and durability:** Multiple copies of data are stored on distinct servers to maintain availability if a disk fails. * **Security:** Volumes are encrypted at rest by default (AES-256-XTS, with a unique key per volume). * **Flexible volume management:** Teams can create, attach, resize, detach, and reattach volumes to instances within the same zone. Resizing is grow-only and can only be performed when the volume is detached, or the instance is stopped. * **Snapshots:** Incremental snapshots support backup and recovery workflows by storing changes after the initial snapshot, with a maximum of 20 snapshots per volume. Snapshots can be used to create new volumes but are not exportable. * **Independent storage:** Volumes remain separate from instance-local storage and persist across reboots, so that volumes survive instance deletion and can be moved to another instance. * **Pricing:** Both active volumes and stored snapshots are billed per GiB-hour. Typical use cases include databases and other I/O-intensive applications that require persistent storage. For stateful Kubernetes workloads, the Exoscale Container Storage Interface (CSI) Driver provisions and manages block volumes as Persistent Volumes. ## How Block Storage Works Each block receives an address that the storage system uses for subsequent read and write operations. The process follows three steps: 1. **Split:** Data is divided into individual blocks 2. **Store:** Each block is stored independently and mapped to its address 3. **Access:** The operating system uses these addresses to locate and retrieve data instantly ![how block storage works](https://www.exoscale.com/blog/what-is-block-storage/block-storage-how-it-works.png) Additionally, a file system can operate on top of this structure. A file system is an extra software layer that organizes data stored on a block storage volume into files and directories. Block storage itself does not provide this file-based organization. When a file system is added, the server's operating system can use it to access and manage the organized data, while the file system keeps track of how this data is mapped to the underlying blocks. ## Key Benefits of Block Storage for Enterprises For enterprises, block storage provides efficient data management and flexible capacity scaling. These characteristics make block storage suitable for workloads that require consistent, responsive data access, as well as environments where storage capacity must scale independently of compute resources. * **Low-latency access:** Direct block-level access supports performance-critical workloads such as databases and virtual machine (VM) disks, which perform frequent read and write operations and require responsive data access. Block storage allows individual blocks to be accessed and modified independently, enabling storage operations to target only the data required for a given read or write request. * **Efficient updates:** Storage systems can modify individual blocks when data changes. Updating only the affected blocks can reduce unnecessary write operations compared with rewriting larger data structures. * **Independent capacity scaling:** Organizations can increase storage by adding or resizing volumes without scaling compute resources at the same rate. Storage capacity can therefore grow without requiring a proportional increase in compute capacity. ## Common Use Cases for Block Storage Block storage is particularly relevant when applications perform frequent input/output (I/O) operations, defined as reading data from and writing data to storage. This requires data to remain available independently of individual compute instances or containers. ### Databases and transactional workloads Database systems use block storage for persistent data files, transaction logs, and more. Database workloads often involve targeted updates to specific portions of stored data. ### Virtual machines Block volumes can serve as boot volumes for virtual machines, storing the operating system and its associated system data. They can also provide persistent storage for application data, allowing data to remain available independently of the lifecycle of the virtual machine instance. Block storage provides direct access to the stored data, allowing the virtual machine to perform read and write operations on its operating system and application data. However, on Exoscale, instances boot from local storage, not from block storage. ### Containers and stateful workloads Stateful containerized applications are applications that need to retain data between container restarts or replacements, such as databases and other applications that store persistent data. Persistent Volumes provide storage that remains available independently of an individual container. Block storage can provide the underlying storage for these volumes, allowing applications to retain persistent data while containers are restarted, replaced, or rescheduled. ## The Architecture of Block Storage Explained A block storage architecture defines how compute resources access storage volumes, how storage is connected to those resources, and how data is protected against storage failures and prepared for recovery. Key components include host access, network-based storage, redundancy, and data protection mechanisms such as snapshots and backups. ![architecture of block storage](https://www.exoscale.com/blog/what-is-block-storage/block-storage-architecture.png) ### Host access A host is a server or virtual machine that accesses a block storage volume through its operating system. The host uses the volume as a block device for applications and file systems. Generally, a block volume is attached to a single host, but it can rarely be attached to multiple hosts. When multiple hosts access the same volume, coordinated access is required to prevent conflicting writes. Clustered file systems coordinate access at the file system level, while application-level locking coordinates access at the application level. ### Network-based or cloud-based block storage A storage area network (SAN) provides block storage over a network and allows hosts to access remote block devices. Cloud block storage uses the same fundamental model, with block volumes attached to compute instances while the underlying storage infrastructure is managed by the cloud provider. ### Redundancy Data is automatically replicated across multiple physical servers (at least twice on Exoscale) within the availability zone. This provides fault tolerance when individual storage components fail. ### Snapshots and backups Block storage uses two primary approaches for data protection: snapshots and backups. Snapshots capture a volume's state at a specific point in time, while backups create separate copies of data for recovery and longer-term retention. Snapshots are either crash-consistent, capturing storage state without application coordination, or application-consistent, coordinating with the application or operating system to capture data in a consistent state. ## Block Storage as a Service: The Managed Model and Where It Fits Block storage as a Service provides block volumes through a managed service platform. The provider operates the underlying storage infrastructure, while customers provision and manage volumes through the service interface. This model reduces the operational effort associated with deploying and maintaining dedicated storage infrastructure. The model characteristics of Block Storage as a Service: * **Managed infrastructure:** The provider operates and maintains the underlying storage platform, including hardware and storage software. * **On-demand provisioning:** Customers create, resize, attach, detach, and delete volumes through the service platform as requirements change. * **Independent scaling:** Storage capacity is scaled independently of compute resources as workload requirements change. * **Performance options:** Providers may offer different volume types or service tiers with defined characteristics such as throughput and input/output operations per second (IOPS). * **Data protection options:** Depending on the provider, the service may include features such as replication, snapshots, backups, or other mechanisms for data protection and recovery. * **Service-based pricing:** Costs may be based on provisioned capacity or actual usage, with additional charges depending on the provider and service configuration. Block Storage as a Service is commonly used in cloud environments, cloud migrations, and hybrid infrastructures where organizations require storage without operating the underlying infrastructure themselves. It is particularly relevant when storage requirements change over time or when organizations want to scale storage independently of their compute resources. ## Checklist: How to Choose Block Storage Choosing a block storage solution requires organizations to match storage characteristics with workload requirements and operational priorities. **1. Workload profile: I/O behavior and demand** * Determine whether I/O is primarily random or sequential, whether reads or writes dominate, and which block sizes and queue depths characterize the workload. * Distinguish between sustained demand and short performance bursts. **2. Performance requirements: Latency, IOPS, and throughput** * Define requirements for latency, input/output operations per second (IOPS), and throughput based on the workload. * Prioritize the metrics that have the greatest impact on application performance. **3. Capacity and scaling: Volume design and future growth** * Determine whether one larger volume or multiple volumes better support the workload. * Plan for capacity growth and consider how scaling may affect storage performance. **4. Cost drivers: Capacity, performance, and retention** * Account for provisioned capacity, selected performance tiers, and expected storage growth. * Include snapshot and backup retention when evaluating ongoing storage costs. **5. Resilience requirements: Availability and recovery** * Define availability and durability targets according to workload requirements. * Establish snapshot and backup strategies and verify recovery procedures through restore testing. **6. Operations and governance: Control and visibility** * Evaluate monitoring and automation capabilities required for ongoing storage operations. * Establish cost controls to identify growth and manage storage expenditure. **7. Security requirements: Encryption and access control** * Verify encryption requirements for data at rest and in transit. * Assess key management and enforce least-privilege access according to organizational security policies. Shortlist solutions that meet the workload, performance, and resilience requirements first. Then validate capacity, cost, operational controls, and security requirements before selecting a storage configuration for production. ## Block Storage for Modern Workloads Block storage is ideal for applications requiring low-latency I/O, durable volumes for databases or virtual machines, or scalable storage capacity independent of computing resources. Before choosing a solution, teams should validate latency, IOPS, and throughput requirements, recovery procedures, host access patterns, and ongoing storage costs. ## FAQ about Block Storage ### What is block storage? The definition of block storage describes a storage model in which data is divided into individually addressable blocks for direct access. These blocks are typically organized into volumes, which operating systems can format with file systems and use as storage devices. ### What is the difference between block storage and a volume? Block storage describes the underlying storage model in which data is stored as independently addressable blocks. A volume is a logical collection of these blocks that the storage system presents to a host as a storage device. ### Is an SSD “block storage”? SSD is the hardware; a cloud volume is a network block device built on many SSDs. ### What is block storage best suited for in enterprise environments? Block storage is particularly suitable for workloads that require persistent storage, low latency, and frequent read and write operations. Common examples include databases, virtual machines, stateful container applications, and performance-sensitive analytics workloads. ### Why can block storage be more expensive than other storage options? Block storage can involve higher costs because providers may allocate dedicated capacity, performance resources, replication, and recovery features. Pricing can also depend on provisioned performance tiers, retained snapshots, backup capacity, and continued storage growth. On Exoscale, Block Storage is priced flat per GiB, and companies benefit from 5,000 IOPS on every volume. ### Can multiple servers safely access the same block volume at the same time? No, multiple servers cannot access the same block volume; generally speaking, block storage can rarely be attached multiple times. On Exoscale, Block Storage volumes can only be attached to one instance at a time (ReadWriteOnce). A volume can be detached from one instance and attached to another within the same availability zone.