What Is Block Storage?

Block storage is a data storage method that divides information into fixed-size units called blocks, each assigned a unique identifier. Commonly used in SAN, iSCSI, and local disk environments, each block can function as a stand-alone storage volume.

Industry research forecasts global active data center capacity to increase sixfold between 2025 and 2035. Applications that depend on databases, virtual machines, and transactional processing demand storage that responds in microseconds, not milliseconds. Traditional file-based approaches often introduce overhead that slows performance at scale. 

Block storage addresses these demands head-on. This data storage method divides information into fixed-size units called blocks, each assigned a unique identifier. Unlike file storage, which organizes data in hierarchical directories, or object storage, which packages data with rich metadata, block storage strips away everything except the raw data and a minimal address. The result is a lean, high-performance architecture optimized for speed. 

Because each block functions as an independent storage volume, operating systems treat them the same way they treat a locally attached hard drive. This makes block storage the foundation for storage area networks (SANs), cloud compute instances, and virtually any workload where low latency and high throughput are non-negotiable.

How does block storage work?

With block storage, each block contains a specific amount of data, typically 256KB to 4MB. Each block represents a portion of a file that isn’t organized in any specific hierarchical order. In fact, the data on blocks sitting beside neighboring blocks may be completely unrelated to each other.

Each block has its own unique identifier—a logical block address (LBA)—that differentiates it from other blocks. When a file needs to be retrieved, an application will send a request, and the storage system consults a lookup table that maps each block’s address to its physical location. The relevant blocks are located, potentially across multiple devices, and reassembled in the correct order. The entire process is transparent to the application.

Besides the identifier, the blocks don’t contain any metadata. Because of the lack of metadata, block storage is very efficient since almost all the block’s storage capacity stores the actual data. There’s no wasted space. This makes block storage ideal for workloads that require rapid scale-up and fast read/write performance.

Storage protocols

Block storage devices communicate with servers through several protocols:

• Fibre Channel (FC): A high-speed, dedicated fabric protocol delivering up to 128Gbps throughput. FC remains the standard for mission-critical SAN environments where performance and reliability are paramount.
• iSCSI: Encapsulates SCSI commands in TCP/IP packets, enabling block storage access over standard Ethernet networks. More affordable than FC, with 10/25/100GbE options closing the performance gap.
• NVMe over Fabrics (NVMe-oF): Extends NVMe’s low-latency, high-queue-depth architecture across network fabrics, delivering near-local performance for shared storage.
• Fibre Channel over Ethernet (FCoE): Converges FC and Ethernet traffic onto a single network, reducing infrastructure complexity while maintaining FC-level reliability.

Block storage vs. file storage vs. object storage

Block storage excels where applications require direct, low-level access to storage volumes with predictable performance. File storage makes more sense for shared collaboration workflows. Object storage is the go-to for massive-scale unstructured data—think media archives, backups, and AI training data sets.

Many enterprises use all three. A typical environment might run databases on block storage, share project files through NAS, and archive cold data to an object store.

Examples of block storage

Directly used by an operating system and available as volumes, block storage can carry out a wide range of tasks. In fact, block storage is the most popular type of storage for most applications.

Some popular use cases for block storage include:

• Database storage: A database typically contains many tables, which are themselves collections of data. Using block files to store this data is ideal since they allow for fast data access. Since speed is critical for a database, organizing the data into blocks is the best solution.
• Disaster recovery: In the event of a disaster, it’s often necessary to restore data from backups. Organizations often use block storage to create block-level backups of data. This allows the data to be restored quickly and easily, with no time-consuming restoration of individual files.
• Mission-critical applications: Mission-critical applications, such as Oracle, Microsoft Exchange, SAP, and Microsoft SharePoint, require high availability and reliability. Using block storage can help ensure that these applications are always available because of block storage’s fast read/write performance.

Advantages of block storage

Like any technology, block storage has its pros and cons. That said, the advantages of block storage are clear: It's best suited for high performance and fast data access.

Here are the key benefits of using block storage:

• Low latency and high IOPS: Modern all-flash block storage arrays deliver response times below 150 microseconds and can sustain millions of IOPS. This is critical for latency-sensitive applications like financial trading platforms, real-time analytics, and healthcare electronic health records.
• Ability to make incremental changes: With block storage, it’s possible to change a file without having to remove all the current data, as you would with a traditional file system. For example, you can make changes by replacing, deleting, or inserting blocks. This makes it ideal for frequently updated files, such as those used in databases.
• Operating system independence: Block volumes can be formatted with any file system—NTFS, ext4, XFS, ZFS—making block storage compatible with Windows, Linux, and other environments simultaneously.
• High availability: Block storage systems commonly use RAID arrays, synchronous replication, and active-active clustering to eliminate single points of failure and maintain uptime during hardware failures.

Disadvantages of block storage

Of course, block storage also has its drawbacks. There's no denying that it can be more expensive than other forms of storage, and it may not be the best solution for all workloads.

Some disadvantages of block storage include:

• Higher cost: Block storage infrastructure, particularly Fibre Channel SANs, requires specialized hardware, including HBAs, FC switches, and dedicated cabling. Cloud block storage also tends to cost more per GB than object or file alternatives. Block storage can be more expensive than other forms of storage. For example, SANs can be expensive to purchase and maintain.
• Management complexity: Configuring and maintaining SANs, LUN masking, zoning, and multipath I/O requires specialized skills. Organizations without dedicated storage administrators may find the operational overhead significant.
• Limited metadata: Block storage’s minimal metadata makes it difficult to search or classify data at the storage layer. Applications must handle metadata management independently.
• Scalability ceilings for unstructured data: While block storage scales well for structured workloads, it becomes harder to manage at petabyte scale. Object storage is typically more cost-effective for massive unstructured data sets.

Implementation best practices

Deploying block storage effectively requires planning around performance, availability, and growth:

1. Assess workload requirements first. Map each application’s I/O profile—random vs. sequential, read-heavy vs. write-heavy, latency sensitivity. This determines whether FC, iSCSI, or NVMe-oF connectivity makes sense.
2. Design for redundancy from the start. Implement RAID protection, multipath I/O, and dual-fabric SAN configurations. For business-critical workloads, consider active-active replication across sites.
3. Right-size your volumes. Overprovisioning wastes capacity and budget. Underprovisioning creates bottlenecks. Modern platforms with thin provisioning and data reduction (deduplication and compression) help optimize effective capacity.
4. Plan for growth with tiered storage. Tier high-performance workloads on NVMe flash and lower-priority data on capacity-optimized media.
5. Automate where possible. Use storage management APIs, infrastructure-as-code tools, and AIOps platforms to reduce manual configuration and accelerate provisioning.

The future of block storage

Block storage continues to evolve alongside the workloads it supports. Several trends are shaping its near-term trajectory:

• NVMe-oF adoption is accelerating. As data centers upgrade to 25/100/400GbE fabrics, NVMe over Fabrics is replacing legacy protocols for new deployments, delivering near-local NVMe performance over network distances.
• Unified storage platforms are blurring the lines. Modern arrays now deliver block, file, and object storage from a single platform, eliminating the need to manage separate silos.
• Storage-as-a-service models are gaining ground. Consumption-based pricing for on-premises block storage eliminates large capital expenditures and aligns costs with actual usage.

How Everpure can help 

It's no secret that data is becoming more and more important by the day, but traditional storage solutions can no longer keep up. Not only are they slow and unreliable, but they can also be expensive.

Everpure offers a better way. Our all-flash block storage products, such as FlashArray//C™, FlashArray//X™, and FlashArray//XL™, are designed for performance, simplicity, and reliability. 

An all-flash array (AFA) contains only flash memory drives in place of spinning disk drives and offers:

• Speed: Quicker memory read/write and access times deliver improved performance and speed. 
• Portability: As solid-state drives (SSDs) are remarkably smaller than more traditional hard-disk drives (HDDs), flash memory has a space-per-capacity advantage.
• Durability: SSDs are less vulnerable to shocks and drops than spinning disk drives.

To learn more about how Everpure can help you get the most out of your block storage, contact us today.