Block storage, also called block-level storage, is a type of IT storage typically used in storage area network (SAN) environments. Data is stored in volumes, also referred to as blocks. The volumes are treated as individual hard disks, so block devices can be mounted by guest operating systems as if they were physical disks.
Block storage works well for storing a variety of applications, including databases, email servers and other high-performance, low latency applications. Any application which requires service side processing, like Java, PHP, and .Net, requires block storage. Adding distance between the application and storage kills the performance advantage due to latency, so most block storage is locally attached. Block storage devices may be more complex and expensive than file storage devices, but they usually provide better performance. For applications with very large files, such as databases, a block storage architecture is more appropriate than file storage to maintain satisfactory performance.
Software-defined storage (SDS) apps can run on industry-standard hardware and enable users to upgrade the software separately from the hardware. SDS makes block storage more affordable and agile than SANs running on proprietary hardware that is tightly coupled to its software. Many SDS products are able to run on Linux and in a virtual machine, on premises or in the cloud. Open source software-defined storage is freely available through community development projects such as Ceph and others. SUSE Enterprise Storage is an SDS management solution powered by Ceph, an OpenStack distributed storage app. SUSE Enterprise Storage provides a single unified SDS cluster for both object storage and block storage.