E-4
About RAID
Using parity minimizes the storage cost of redundancy. Because
only one drive is used to store parity, a three-drive array, which is
the worst case, uses only one-third of the total capacity for
redundancy. In larger arrays, the storage cost of redundancy
decreases proportionately.
RAID 5 write performance is limited by the need to generate parity
data for every write. Read performance is good because the load is
spread equally across all the drives.
RAID 10
This dual-level RAID type is created by using two or more equal-
sized RAID 1 arrays to create a RAID 0. Both read and write
performance are improved due to array striping. However, the
performance improvement costs additional storage space due to
the mirroring of the arrays.
Drive
RAID 1
RAID 1
Top-Level Arrays
Second-Level Arrays
Data 2
Data 4
Data 6
RAID 10
Data 2
Data 4
Data 6
Data 0
Data 2
Data 4
Data 6
Data 0
Data 3
Data 5
Data 7
Data 1
Data 3
Data 5
Data 7
Data 1
Data 3
Data 5
Data 7
Data 1
Drive
Drive
Drive
Data 0
