NEC SigmaBlade AD106a Guide de l'utilisateur télécharger pdf (Page 51)

Configuring Your Storage and I/O Blade 4-7

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)

1 2 ... 46 47 48 49 50 51 52 53 54 55 56 ... 161 162

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NEC SigmaBlade AD106a Guide de l'utilisateur Page 51