Introduction and Comparison of hardware and software and RAID BIOS

Terms

RAID
An independent redundant disk array is a storage term. to improve performance and reliability, multiple disks are combined, which is a storage unit from the outside. the detailed introduction to RAID is not within the scope of this document; Wikipedia article "RAID" provides better content.

Hard RAID
Hard RAID is a RAID ("RAID card") implemented in the storage controller ")
Through the unique hardware and firmware. the Controller BIOS provides interfaces for managing RAID installation. for system-level applications, RAID looks like a single storage device like a SCSI hard disk. therefore, the operating system can use RAID as a storage device through a standard driver. if you need to configure RAID and monitor the display of physical disks, you need to use proprietary drivers.

Soft RAID
Soft RAID is implemented by software and operating system drivers independent of the storage controller. This driver is responsible for configuring and managing RAID.
On Linux, soft RAID is implemented through the md (multiple devices) kernel driver and mdadm management tool. linux soft RAID uses its own format to store RAID configuration information (referred to as "meta information ").

BIOS RAID
Bios raid (referred to as "quasi-hard RAID") is a form of Soft RAID. its RAID configuration management is partly or entirely completed by the storage controller, but it is not a real hard RAID. to enable bios raid to work properly, you need to install a driver in the operating system.
Bios raid is often referred to as "pseudo RAID" because it is easily mistaken for hard RAID. generally, the vendor that provides this bios raid function in the storage controller seldom informs the purchaser that this is not a hard RAID, in addition, it needs to load a dedicated driver in the operating system to make it work normally. A relatively reasonable description of the term should be "BIOS-assisted soft RAID ".

Hard comparison, soft and BIOS RAID
Comparison between hard RAID and soft RAID: this comparison is beyond the scope of this document.

Comparison between bios raid and hard RAID
Bios raid requires a dedicated driver to work; hard RAID is not required. using a proprietary driver may make data recovery very complex. For example, the system cannot boot.
For bios raid, the CPU is used to manage the RAID structure. For hard RAID, all these are the responsibility of the storage controller, and the CPU is not involved in RAID maintenance.

Comparison between bios raid and Linux soft RAID
Bios raid is limited to connecting to a storage device that provides a bios raid storage controller. for Linux soft RAID, RAID can be used on multiple block storage devices, including storage devices connected to the storage controller but not supporting the RAID function, or connect to storage devices on different storage controllers.

For bios raid, a dedicated driver is required to work properly, while Linux soft RAID can be implemented through a standard driver (md ).
The structure of bios raid on the storage device varies with the vendor. if the storage controller is invalid, you must use a storage controller of the same specification to access data on RAID. for Linux soft RAID, the structure set on the storage device is independent from the disk controller. If the RAID cannot be managed due to the Controller defects, you can use another controller to obtain data again, it does not need to be a storage controller of the same specification.

Data stored in bios raid can be easily accessed in Microsoft Windows in Linux + Windows.