Bull NovaScale T860 E1, User Manual

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RAID1
In the RAID1 level, data saved in a HDD is written to another HDD without changes. This mode is called "mirroring".
When data is written onto a single HDD, the same data is written onto another HDD. If either one of the HDDs is
defective, the other HDD containing the same data can replace the defective HDD. Thus, the system can continue to
operate without interruption.
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 of the
HDDs configuring a logical drive is defective, data is still available.
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)