What is block storage? | Definition from TechTarget

What is block storage?

Block storage is a data storage method where each volume acts as an individual hard drive configured by the administrator.

In the block storage model, data is stored on storage media in fixed-sized chunks called blocks. Each block is associated with a unique address, and the address is the only metadata provided for each block.

To manage block storage, a software program independent of the storage media controls how blocks are placed and organized on storage drives. The software also manages data extraction, using metadata to find the desired blocks and then organizing its data into complete files.

Storage blocks are controlled by the server-based operating system and are typically accessed by iSCSI, Fiber Channel or Fiber Channel over Ethernet protocols. Block storage is ideal for high-performing, mission-critical applications that require consistent input/output performance and low latency and is often used in storage-area network (SAN) environments in place of file storage.

Because block storage plays an important role in many business applications, some cloud vendors offer block storage services in addition to their object storage services. Popular cloud block services include Amazon Elastic Block Store (EBS), Google Cloud Persistent Disks and Rackspace Cloud Block Storage.

Block storage devices

Block storage remains at the forefront of areas, supporting mission-critical and data-intensive tasks. But this seems to be changing. Increasingly, organizations are turning to the cloud for block storage as they seek more efficient and flexible ways to support their workloads.

Since block storage volumes are treated as individual hard disks, the method is ideal for storing different applications:

  • Email servers such as Microsoft Exchange use block storage instead of file- or network-based storage systems.
  • With RAID arrays, multiple independent disks are combined together for data protection and performance. Block storage’s ability to create individually controlled storage volumes makes it a good fit for RAID.
  • Virtualization vendors such as VMware support block storage protocols, which can improve migration performance and improve the scalability of the VM file system. Using SAN for block storage also helps with VM management, enabling non-standard SCSI commands to be written.

Blocking against file storage

While there are benefits to using block storage, there are also alternatives that may be better suited to certain organizations or uses. Two options appear when it comes to dealing with block-level storage: file storage and object storage.

If simplicity is the goal, file storage may win out over block-level storage. But while block storage devices are more complex and expensive than file storage, they also tend to be more flexible and provide better performance.

File storage provides a centralized, easily accessible location for files, and generally comes at a lower cost than block storage. File storage uses metadata and directories to organize files, making it a convenient option for an organization looking to store large amounts of data.

The relatively easy deployment of file storage makes it a practical tool for data protection, and the low cost and simple organization help with local archiving. File sharing within an organization is another common use for file storage.

The simplicity of file storage can also be its downfall. While it has a hierarchical organization to it, the more files added, the more difficult and tedious it is to sift through the file storage. If performance is the deciding factor, object or block-level storage wins over file storage.

Some products, such as Hewlett Packard Enterprise (HPE) 3PAR File Persona Software, converge on file and block storage to provide the benefits of both technologies.

Blocking against object storage

Instead of dividing files into raw blocks of data, object storage bundles data as an object with data and metadata. Storage blocks have no metadata, so object storage provides more context about the data, which helps classify and customize files. Each item also has a unique identifier, making it easier to find and retrieve items from storage.

Block storage is scalable, but object storage is unmatched when it comes to scalability. Scaling an object storage architecture simply requires adding nodes to the storage cluster.

object vs. block storage vs.  file storage

The flexibility and scalability of object storage can be attractive, but some organizations may want to prioritize performance and choose file or block storage. While block storage enables editing of incremental parts of a file, store objects must be edited as a unit. If a part of an object needs to be edited, the entire object must be accessed and updated, then rewritten, which can negatively affect performance.

Both object and block-level storage are used in the enterprise, but the object storage use case leans more toward scenarios involving large amounts of data, such as large data storage and backup archives. Because of this, modern data storage environments such as the cloud tend to be trending towards object-based storage in file and block storage options. However, individual needs will often determine which form of storage is used.

Block storage vendors

Along with HPE, many large and small storage vendors provide block storage. The largest storage vendors are Dell, Hitachi Vantara, IBM and NetApp. Additional vendors include DataDirect Networks, Huawei, Infinidat, Nutanix, Oracle, Pure Storage, Tintri and Western Digital. The biggest vendors all have multiple block storage platforms, as well as integrated storage that runs block and file on the same arrays.

OpenStack Block Storage (Cinder) is an open source form of block storage, which provisions and manages storage blocks. It also provides basic storage capabilities such as snapshot management and replication. OpenStack Block Storage is supported by other vendors such as IBM, NetApp, Rackspace, Red Hat and VMware.

Amazon EBS is the persistent block storage for the Amazon Elastic Compute Cloud. EBS is scalable and designed for workloads such as big data analytics, NoSQL databases and data warehousing.

Why block storage is gaining momentum

With major vendors such as Dell and Amazon on board with block storage products, it is clear that this is a supported technology for the foreseeable future. While there are pros and cons to using it, many of the negatives can be chalked up to features that are better provided by a different storage system. These needs may vary by organization, and while file or object storage may be more appropriate in some cases, block storage may be the right choice for others.

If an organization is looking to incorporate the cloud, then they will find block storage to be a common partner for cloud computing.

The main disadvantage of SAN environments, where block storage systems are often found, is the cost and complexity associated with building and managing the environment. As long as organizations are willing to face the obstacles, SAN environments will remain a viable option. With virtual and converged SAN options on the market today, SAN arrays — and block storage with them — will likely continue to grow and meet consumer needs.

Editor’s note: This article was revised in 2023 by TechTarget editors to improve the reader experience.

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