What is block storage? All you need to know

Block storage is a storage tech­no­logy in which data is divided into equally sized blocks and stored in­de­pend­ently. These blocks can be directly addressed via addresses, enabling par­tic­u­larly fast access times and high per­form­ance. This makes the ar­chi­tec­ture ideal for databases or virtual machines.

What is block storage?

While with file storage, entire files are stored in a folder system, data in block storage—unlike object storage—is stored in the form of blocks. These blocks are stored where the system deems most ap­pro­pri­ate. It divides files evenly into blocks, causing the files to lose their original sig­ni­fic­ance and making them unable to be easily executed or opened. Blocks are units of equal size. To ensure in­di­vidu­al blocks can be found again, each block is assigned an address. When the server receives a request, it can then locate, re­as­semble, and deliver the data.

How does block storage work?

Block storage is commonly used within a Storage Area Network (SAN). In this setup, multiple servers can access data over a network, with software managing the precise location of each data block. Ori­gin­ally, block storage in SAN en­vir­on­ments resembled a LAN, using com­pon­ents like switches and hubs. Today, however, block storage can also be deployed in cloud en­vir­on­ments — a model often called block-level storage. Here, a tra­di­tion­al system of hard drives is virtually rep­lic­ated.

Com­mu­nic­a­tion in a SAN usually happens via Fibre Channel (FC) or Internet Small Computer System Interface (iSCSI). FC is an interface designed for very high-speed trans­mis­sions. In contrast, the iSCSI method uses TCP and Ethernet, making it easy to integrate into existing networks.

Modern cloud providers use block storage as a flexible found­a­tion for virtual machines or per­sist­ent container-volumes. The storage blocks are often managed via cloud-based ad­min­is­tra­tion APIs, enabling dynamic and automated pro­vi­sion­ing in DevOps and Kuber­netes-en­vir­on­ments.

Ad­vant­ages and dis­ad­vant­ages of block storage

Compared to other forms of data storage, block storage is con­sidered par­tic­u­larly fast and highly redundant. Each block has an in­di­vidu­al address through which the data can be accessed. Other storage methods rely on metadata, sometimes in very large quant­it­ies. The absence of this ad­di­tion­al in­form­a­tion can be both an advantage and a dis­ad­vant­age. While the blocks remain very lean and can be directly accessed, if you want to de­lib­er­ately store metadata, an ad­di­tion­al database is necessary. The biggest dis­ad­vant­age of block storage is the cost, as SANs rely on expensive hardware.

Ap­plic­a­tions of block storage

Block storage showcases its ad­vant­ages, es­pe­cially in databases. The reason lies in the high speed with which data can be both read and written. Trans­ac­tion­al databases need constant ad­just­ments. Block storage delivers excellent results here, whereas other storage methods often involve delays. This is not ideal for business ap­plic­a­tions. Block-level storage is also used in virtual machines. The tech­no­logy makes it easy to provide storage for vir­tu­al­isa­tion.

Moreover, block storage also plays an in­creas­ing role in con­tain­er­ised ap­plic­a­tions. Per­sist­ent volumes can be ef­fi­ciently pro­vi­sioned through block-based storage solutions and are ideally suited for stateful workloads like databases or search indexes.