RAID 3, data is stored on n-1 discs., where data is striped across multiple discs at a byte level. The parity information is stored on dedicated parity disc, but failure at any disc can be accepted. Parity disc very often is considered to be a bottleneck, especially for random writes as it is need to be accessed any time data is sent to array. RAID 5 in comparison to RAID 3 improves write performance by using distributed parity. RAID 3 differs from RAID 4 only the size of the stripes stored on various discs.

Controller Requirements: medium to high end hardware RAID card
Hard Disk Requirements: minimum 3 hard drives, maximum is set by controller, all the discs should be the same size.
Array Capacity: size of the smallest drive*(number of drives -1)
Storage Efficiency: (number of drives -1)/number of drives
Fault tolerance: good, loss of one drive can be tolerated
Availability: very good, most of controllers support automatic rebuild and hot sparing
Degradation and rebuilding: rebuilds can take many hours, relatively little degrading of performance in case of disc fail
Random read performance: good, because of byte level striping
Random write performance: poor, because of byte level striping, bottleneck of the parity disc and parity calculations
Sequential read performance: very good
Sequential write performance: fair good