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2. RAID Levels
This section details the RAID levels which the disk array controller can support.
2-1. Characteristics of RAID Levels
The table below lists the characteristics of the RAID levels.
Level
Function
RAID0
Striping
RAID1
Mirroring
RAID5
Striping of both data and
redundant data
RAID10
Combination of striping
and mirroring
2-2. RAID0
In RAID 0, data to be recorded is distributed to HDDs. The mode is called "striping".
In the figure below, data is recorded in stripe 1 (disk 1), stripe 2 (disk 2), and stripe 3 (disk 3)... in the order.
Because RAID0 allows all HDDs to be accessed collectively, it can provide the best disk access
performance.
RAID 0 does not have data redundancy. If a HDD is defected, the data
saved in the HDD cannot be recovered.
Notice
2-3. RAID1
In the RAID1 level, data saved in a HDD is recorded to another HDD without change. This mode is called
"mirroring".
When data is recorded to a single HDD, the same data is recorded to another HDD. If either of the HDDs is
defected, the other HDD containing the same data can substitute for the defected HDD. Thus the system can
continue to operate without interruption.
Redundancy
Characteristics
No
Data read/write at the highest rate
Largest capacity
Capacity: (capacity of single HDD) ×
(number of HDDs)
Yes
Two HDDs required
Capacity: capacity of single HDD
Yes
Three or more HDDs required
Capacity: (capacity of single HDD) ×
((number of HDDs) - 1)
Yes
Four HDDs required
Capacity: (capacity of single HDD) × 2
Disk array controller
Disk 1
Disk 2
Stripe 1
Stripe 2
Stripe 4
Stripe 5
Disk 3
Stripe 3
Stripe 6
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