Configuring Your Server 4-27RAID5In RAID5, data is distributed to HDDs by striping and, at the same time, the parity (redundant data)is distributed to the HDDs. This mode is called "striping with distributed parity".Each of stripe x, stripe x+1, and parity (x, x+1) created from stripe x and stripe x+1 is written onto aspecific HDD. Accordingly, the total capacity assigned to the parity is just the same as the capacityof a single HDD. If any one of the HDDs configuring a logical drive is defected, data is stillavailable with no problems.RAID ControllerHDD 1 HDD 2 HDD 3Stripe 2Parity (3, 4)Stripe 5Parity (1, 2)Stripe 3Stripe 6Stripe 1Stripe 4Parity (5, 6)RAID6A RAID 6 extends RAID 5 by adding an additional parity block (Q) created by different calculationmethod such as weighting by some factor, thus it uses block-level striping with two parity blocksdistributed across all member disks. This mode is called "striping with duplex and distributedparity". Accordingly, the total capacity assigned to the parity is just the same as the capacity of twoHDDs. If any two of the HDDs configuring a logical drive are defected, data is still available withno problems.RAID ControllerHDD 1 HDD 2Stripe 1HDD 3Stripe 4Stripe 2Parity P (3,4)Parity P (1,2)Parity Q (3,4)Parity P (5,6) Parity Q (5,6) Stripe 5HDD 4Parity Q (1,2)Stripe 3Stripe 6Parity Q (7,8) Stripe 7 Stripe 8 Parity P (7,8)
