All storage systems have a controller, which is a device with a processor that sends instructions to the disks. Storage controllers differ from vendor to vendor, but generally fit into three types — custom designed, purpose-built, and commodity server-based.
Each type of implementation has advantages and drawbacks. Vendors will highlight the characteristics of what their systems offer. It is up to customers to do the evaluation to determine what system best fits their needs.
These are the key characteristics for each type of storage controller:
Custom designed storage controllers have hardware that is specific for that storage system. Custom ASICs (Application Specific Integrated Circuits) orFPGAs (Field Programmable Gate Arrays) are common in custom controllers. They might also have custom logic or use standard components such as Intel processors. Storage software exploits the custom hardware.
Performance and reliability are the two major advantages of a custom controller design. Performance acceleration comes from using custom hardware for data movement, RAID protection, compression, encryption, or other processing intensive operations. Reliability improvements come from built-in error checking and a reduction in number of components required.
The disadvantages are that it is usually costs more to implement a custom design and it takes the vendor longer to develop a new or updated storage controller.
A purpose-built storage controller uses commonly available elements such as processors and adapter boards integrated into a package. The storage software has an understanding of the specific hardware in a configuration.