Raid Level 0: Implements a striped disk array, the data is broken into blocks, & each block is written to a separate disk drive. Uses entire disk capacity. Minimum two drives are required to implement.
Applications: Video & image processing.
Advantages: Improved performance for Input/Output operations as the I/O load is distributed across several channels & drives. Best performance is delivered as data is striped across multiple controllers with only one drive per controller. Provides high-speed improvement, particularly for write operations as read & write requests both are evenly distributed across all the disks in the array. Less overhead as no priority calculations. Implementation is easy. Design is simple & it is cheap.
Disadvantages: Does not provide fault tolerance. Results in complete data loss as a result of failure of just one drive. Not suitable for mission critical environment.
Raid Level 1: The drawback of RAID 0 of no fault tolerance is removed in RAID 1. Fault tolerance is provided by mirroring the data. It does not facilitate striping. Minimum two HDD's are required. The data written to both the disks is transparent to the host. If the first disk fails to provide data, the mission drive is used by the RAID controller for data recovery & contiguous operation.
Advantages: Provides high availability & data protection. To provide high performance, the controller needs to perform two concurrent reads & write operations per two drives. One Write & two reads are possible per mirrored pair. Provides 100% redundancy. Hence in case of disk failure, data from mirrored drive is just copied & the failed disk is replaced. Design is simple.
Disadvantages: It has high disk overhead. When unimplemented using S/o, does not support hot swap of failed disk.
Applications: Banking Application,Payroll Management,Applications which require high availability.
Raid 5: In RAID 5 the parity is distributed across all the disks. RAID 5 is secure & fits to a large, reliable & relatively cheap storage. Minimum three disks can be used to realize RAID 5 level. The parity is used to reconstruct the data of one of the failed disk whose data no longer be available.
Advantages: I/O rate for read operation is quite fast whereas I/O rate for write operations are slightly slow. All data is accessible even if a drive facts, which gives sufficient time to replace the failed drive & the storage controller can rebuild the data on the new drive.
Disadvantages: Throughput is affected whenever a drive fails. RAID 5 is complex technology.
Applications of RAID 5: Transaction processing, File & Print servers, Database operations, Emails, etc.