Scalability is the ability for IT systems – such as applications, storage, databases and networking – to continue to function properly when changed in size or volume. It often refers to increasing or decreasing resources as needed to meet the higher or lower demands of a business.
Vertical (scale-up) scalability increases the capacity of hardware or software by adding resources to a physical system, such as adding processing power to a server to make it faster. For scale-up storage, this means adding more devices, such as disk drives, to an existing system when more capacity is required.
Horizontal (scale-out) scalability connects multiple items in order to work as a single logical unit. For scale-out storage, this means adding devices in connected arrays or clusters. Each cluster can have many nodes (devices), and nodes can be separated geographically. Scale-out NAS (network-attached storage) grows by adding clustered nodes. Because each node includes storage capacity, processing power and I/O (input/output) bandwidth, performance increases along with storage capacity. In a scale-out storage system, new hardware can be added and configured as the need arises. When a scale-out system reaches its storage limit, another array can be added to expand the system capacity. Scale-out storage can use the added storage across arrays. A scale-out architecture allows the initial storage investment to be small, because future storage can be added as needed.
Software-defined storage (SDS) creates a virtualized network of storage resources by separating the management software from its underlying storage hardware. SDS resources may be spread across multiple servers and shared as if they reside on one physical device. This type of storage enables unlimited scalability on demand. SUSE Enterprise Storage is an SDS solution that provides limitless storage capacity and scalability.