Disk Arrays and Disk Array Controllers
SAN Recovery - Disk Arrays and Disk Array Controllers
Disk Array
A disk array refers to a disk storage system with multiple disk drives. The components of disk array include disk array controllers, cache memories, disk enclosures and power supplies. It also offers advanced storage functionalities such as RAID and virtualization.
Disk arrays are categorized in to five: NAS, Modular SAN arrays, Monolithic SAN arrays, Storage Virtualization and Utility SAN Arrays.
Components of a disk array offer higher availability, resiliency and maintainability to an extent that all single points of failure (SPOFs) are eliminated from the design. These components (controllers, power supplies, fans, etc.) are hot-swappable too, meaning they can be repaired or replaced even while the system is performing its task.
Disk Array Controller
A disk array controller refers to a device that manages the physical disk drives. Disk array controllers often implement hardware RAID, so they are also known as RAID controllers. Disk array controller also provides additional disk cache.
Disk array controller presents the disk drives as logical units. In today’s enterprise architecture, they are part of disk arrays placed in a storage area network (SAN) or network-attached storage (NAS) servers.
Disk array controller provides both front-end and back-end interfaces. Front-end interface communicates with a computer’s host adapter (HBA) while back-end interface communicates with controlled disk. Common protocols used in front-end interface are ATA, SATA, SCSI, or FC. It may also use protocols (such as FICON, iSCSI, InfiniBand, etc.) dedicated for a specific purpose. Back-end interface uses protocols such as ATA, SATA, SCSI, FC or SAS.
A disk array controller may be fit inside a computer as a PCI expansion card, or it can be built onto the motherboard.
