A RAID controller is a card or chip located among the working system and the storage drives, typically tough disk drives. RAID affords facts redundancy and/or improves hard disk pressure performance; most RAID degrees do both. RAID does offer redundancy on SSDs, but does no longer improve SSD performance.

RAID controllers paintings by means of virtualizing the drives into distinct companies with particular data safety and redundancy characteristics. The front-quit interface communicates with the server, typically through a bunch-primarily based adapter (HBA); and the backend communicates with and manages the underlying storage media; normally ATA, SCSI, SATA, SAS, or Fibre Channel.

RAID controllers card for server are labeled with the aid of multiple traits along with drive types consisting of SATA or SAS, the variety of ports and variety of drives it may support, specific RAID degrees, interface architecture, and what kind of reminiscence exists in native cache. For instance, which means a controller manufactured for a SATA environment will no longer paintings on a SAS array, and that a RAID 1 controller can not be modified into a RAID 10.

RAID controllers aren’t storage controllers. Storage controllers offers active disks to the OS, at the same time as the RAID controller acts as a RAM cache and presents RAID functionality. The quantity and identification of RAID disks depends on a RAID controller’s configuration.

• Hardware-Based: RAID Controller

• Dedicated hardware controllers come in exclusive architectures: an external RAID Controller Card and an inner RAID-on-Chip:
• RAID-on-Chip: Less pricey RAID-on-Chip is a single motherboard chip that integrates the host interface, HDD I/O interfaces, the RAID processor, and a reminiscence controller. Firmware begin up RAID at some point of bootup, then switch control to the drivers.

• Software-Based: Server-Based RAID

• Software RAID provides RAID offerings from the host. It comes in flavors: software program-described hosted in the OS, and a hybrid architecture that contains a hardware aspect to alleviate the weight on the CPU.
• Software-handiest RAID: Software-simplest RAID is normally protected as a native characteristic at the OS, which makes it the least costly of the RAID alternatives. The host-based totally utility manages RAID calculations, and attaches to the storage drives using an HBA or native I/O interface. It starts up while the OS hundreds the RAID driver.
• Hybrid hardware/software RAID: Hybrid hardware/software program RAID uses a hardware component to supply RAID BIOS features from the motherboard or HBA. The hybrid generation adds some other layer and is extra highly-priced the software program-simplest, however it protects the RAID device from boot errors ought to something manifest to the working machine.

• Advantages of RAID Controllers :

The controller structure of hardware-based totally RAID is extra expensive than software program-primarily based RAID, however will increase gadget performance and isn’t problem besides errors.

• Cache memory:. Controller-based totally RAID typically provides additional dick cache reminiscence, which accelerates RAID operations.
• Dedicated processing:. Controller-based systems independently manage RAID configuration other than the OS. And for the reason that RAID controller does no longer require disk processing energy, ability and velocity win out over software-simplest RAID.
• Lack of boot errors:. And considering software program-best RAID is located at the OS, it is challenge as well errors which can compromise a whole array. Boot errors will not have an effect on RAID controllers.

• Advantages of RAID :

RAID is a fundamental statistics safety and driver for HDD and SSD, and a performance driving force for HDD. Top advantages encompass:

• Better reliability :Except for RAID 0, RAID ensures that a unmarried crashed node will no longer take an array down with it. Applications continue to operate on remaining nodes whilst the failed node is repaired or changed, which maintains statistics consistency and guards in opposition to statistics loss.
• Data redundancy:  RAID mirroring and/or striping with parity spreads facts throughout more than one nodes, making sure that no statistics is misplaced should a node fail.

Higher HDD overall performance: Most RAID ranges enhance throughput with the aid of allowing packages to concurrently examine and write information from a couple of drives. This is not an automatic development: higher RAID stages, in particular RAID 10, take up gadget overhead, making them incorrect for low- or mid-overall performance arrays. These arrays benefit maximum from RAID – performance improvement, or RAID 5/6 for overall performance plus redundancy. On a excessive-overall performance array, RAID 10 increases overall performance and affords redundancy and high availability.