what is meant by raid levels.

(Redundant Array of Independent Disks)

RAID is a storage technology that combines multiple disk drives into a logical unit.

It efficiently stores and retrieves the data across multiple hard drives using raid techniques such as striping, mirroring and parity.

Main advantage of RAID, It provides great redundancy, performance, increased bandwidth, and protects the data against hard drive crashes.

Hardware Raid:

Hardware Raid which comes along with a specific hardware disk array called Raid hardware controller. It can be configure on BIOS level of the system.

Raid array adapters/controllers plug into a host bus slot [typically a 133 MB/sec PCI bus]. Arrays are available for mid- to high-end servers due to cost.

Lower-cost bus-based array adapters are now available for entry-level servers.

External Hardware RAID Card Intelligent external array controllers "bridge" between one or more server I/O interfaces and single-or multiple-device channels.

Software Raid:

Here operating system acts as Software Raid controller; it can be implementing OS Kernel level.

The performance of a software-raid depends on the server CPU performance and load.

Striping: Disk striping is the process of dividing data into blocks and spreading the data blocks across several hard disks. which can be as small as one sector (512 bytes) or as large as several megabytes.

Parity: Parity is a combination of data storing in foam of images. The parity drive points to data drives. But if loss parity drives we can’t access the data drives.