what is a raid card

A RAID card, or disk array controller, is a device that manages the physical disk drives and presents them to the computer as logical units. It almost always implements hardware RAID, which stands for redundant array of independent disks, and is a type of data storage virtualization technology that lumps physical disk drive components together to drive data redundancy and/or improvement. A RAID controller can be hardware, such as a PCI or PCI Express (PCIe) card, or software-only, using the hardware resources of the host system, particularly the host’s CPU and DRAM. The primary functions of a RAID controller are to combine multiple low speed or low-capacity storage drives into a single faster and higher volume drive so that they work as a logical unit, and to create redundancy to ensure data usability in the event of drive failure. RAID controllers can be fully configured through card BIOS before an operating system is booted, and after the operating system is booted, proprietary configuration utilities are available from the manufacturer of each controller. There are different types of RAID, as dictated by the Storage Networking Industry Association, including RAID 0, RAID 1, RAID 5, RAID 6, and nested RAID levels.