RAID 5 writes data across all hard drives in the array and a parity block for each data block. If one physical
hard drive fails, the data from the failed hard drive can be rebuilt onto a replacement hard drive. While the
files stored on a RAID 5 array remain intact should one hard drive fail, data can be lost if a second hard drive
fails before the RAID is rebuilt with the replacement hard drive.
A minimum of three hard drives is required to create a RAID 5 array.
RAID 5 offers performance that can approach RAID 0. RAID 5’s strong advantage over RAID 0 is data
protection. Additionally, you still have approximately 75% of the storage capacity of a RAID 0 array (based
upon total available hard drives and storage capacities). The equation for determining the storage is:
The size of the hard drive with the smallest capacity in the array) * (Total hard drives-1)
Example 1: An array is assigned five 3TB hard drives for a total of 15TB. The equation is:
3TB * 4= 12TB.
Example 2: An array is assigned Three 2TB hard drives and one 3TB hard drive for a total of 9TB. The
equation is:
2TB * 3= 6TB.
RAID 6
