What is a RAID Controller?

A RAID controller is also known as a disk array controller, and it is a type of storage component that manages the disk drives in a RAID infrastructure. RAID stands for redundant array of independent disks. A RAID controller is a card or chip located between the operating system and a storage drive (typically a hard drive).  

 A RAID controller has two primary functions: 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. 


How does a RAID controller work?  

A RAID controller works by virtualising drives into distinct groups with specific data protection and redundancy characteristics. The front-end interface typically communicates with the server through a Host Bus adapter whereas the back-end interface manages and communicates with the underlying disks. 

A storage controller presents active disks to the OS, and a RAID controller acts as a RAM cache and provides RAID functionality. So, a RAID controller is not a storage controller.  

A RAID controller manufactured for a SATA environment won’t work on a SAS array. This is because RAID controllers are classified by multiple characteristics such as drive type protocol (SATA or SAS), number of ports and number of drives, interface architecture, specific RAID levels, and how much memory exists in native cache. The identity and number of RAID disks all depends on a RAID controller’s configuration. 


What does a RAID controller do?  

A RAID controller will be highly useful to you or your business if uptime and availability are paramount. While backups will insure you from data loss, restoring large amounts of data (in the event of drive failure, for example) can take many hours to perform. If those backups are hours or days old, you will lose all of the data stored or changed since the last backup. With RAID, you can weather the failure of one or more drives without data loss and, in many instances, without any downtime.  

However, it’s not advised to use RAID as a total replacement for backups because RAID does not deliver 100% uptime (nothing can!). There are seven different levels of RAID to be aware of: 

  • RAID 0: uses disk striping and offers no redundancy – if any of the drives fail, within this level, the RAID unit will fail. 
  • RAID 1: uses mirroring to offer redundancy by writing data identically to two drives. 
  • RAID 5: evenly balances reads and writes by using block-level striping with distributed parity, meaning no single disk will become a bottleneck.  
  • RAID 6: works in a similar fashion to RAID 5, but adds an additional parity block on each disk within the array. 
  • RAID 10: it’s possible to combine levels to produce a two-digit RAID level, so this level is a combination of level 1 and 0 which makes this level resilient and fast at the same time.  
  • RAID 50: this level combines level 5 and 0 which enables this level to offer increased data protection and fast rebuilds.  
  • RAID 60: this level combines level 6 and 0 and is commonly known as dual drive failure protection.  


How to check your RAID controller 

If your PC or server does not have a RAID controller, you can install one. There are different types of RAID controllers - a RAID controller card, a standalone RAID controller unit or even a standalone enclosure. If you want to view the status of your RAID controller, in most cases you will need to install specialised software to do so. 

It’s important to know that RAID can be performed via software or hardware. If you have a hardware-based RAID you can typically find this in the PCIe slot of the PC’s motherboard. Processing occurs on a separate RAID system, unlike with software RAID, which lessens the burden on the system’s CPU. With the software option, RAID is performed via software deployed on an operating system.  

By first identifying your requirements, you can then pinpoint what level/type of RAID controller will be most suitable. In addition to the specific RAID levels as laid out above, RAID controllers are also classified by drive type (such as SATA or SAS), the number of ports and drives it can support, interface architecture, and the amount of memory in native cache. As an example, a RAID controller manufactured for a SAS array will not work in a SATA environment. Additionally, a RAID 1 controller cannot be modified into a RAID 10 controller.  

Browse our range of RAID controllers here or get in touch for more information.