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Configuring Your Server 4-25
RAID Controller
HDD 1 HDD 2
Stripe 1
Stripe 2
Stripe 1
Stripe 2
RAID5
In 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 a specific HDD.
Accordingly, the total capacity assigned to the parity is just the same as the capacity of a single HDD. If any one of the HDDs
configuring a logical drive is defected, data is still available with no problems.
RAID Controller
HDD 1 HDD 2 HDD 3
Stripe 2
Parity (3, 4)
Stripe 5
Parity (1, 2)
Stripe 3
Stripe 6
Stripe 1
Stripe 4
Parity (5, 6)
RAID6
A RAID 6 extends RAID 5 by adding an additional parity block (Q) created by different calculation method such as weighting
by some factor, thus it uses block-level striping with two parity blocks distributed across all member disks. This mode is called
"striping with duplex and distributed parity". Accordingly, the total capacity assigned to the parity is just the same as the
capacity of two HDDs. If any two of the HDDs configuring a logical drive are defected, data is still available with no
problems.
RAID Controller
HDD 1 HDD 2
Stripe 1
HDD 3
Stripe 4
Stripe 2
Parity P (3,4)
Parity P (1,2)
Parity Q (3,4)
Parity P (5,6) Parity Q (5,6) Stripe 5
HDD 4
Parity Q (1,2)
Stripe 3
Stripe 6
Parity Q (7,8) Stripe 7 Stripe 8 Parity P (7,8)