Users Guide
RAID 1 characteristics:
• Groups n + n disks as one virtual disk with the capacity of n disks. The controllers currently supported by Storage Management
allow the selection of two disks when creating a RAID 1. Because these disks are mirrored, the total storage capacity is equal to
one disk.
• Data is replicated on both the disks.
• When a disk fails, the virtual disk still works. The data is read from the mirror of the failed disk.
• Better read performance, but slightly slower write performance.
• Redundancy for protection of data.
• RAID 1 is more expensive in terms of disk space since twice the number of disks are used than required to store the data without
redundancy.
RAID level 5 (striping with distributed parity)
RAID 5 provides data redundancy by using data striping in combination with parity information. Rather than dedicating a physical disk
to parity, the parity information is striped across all physical disks in the disk group.
RAID 5 characteristics:
• Groups n disks as one large virtual disk with a capacity of (n-1) disks.
• Redundant information (parity) is alternately stored on all disks.
• When a disk fails, the virtual disk still works, but it is operating in a degraded state. The data is reconstructed from the surviving
disks.
• Better read performance, but slower write performance.
• Redundancy for protection of data.
RAID level 6 (striping with additional distributed parity)
RAID 6 provides data redundancy by using data striping in combination with parity information. Similar to RAID 5, the parity is
distributed within each stripe. RAID 6, however, uses an additional physical disk to maintain parity, such that each stripe in the disk
group maintains two disk blocks with parity information. The additional parity provides data protection in the event of two disk
failures. In the following image, the two sets of parity information are identied as P and Q.
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