User's Manual

42 Understanding RAID Concepts
RAID Level 1 (Mirroring)
RAID 1 is the simplest form of maintaining redundant data. In RAID 1, data
is mirrored or duplicated on one or more physical disks. If a physical disk on
one side of the mirror fails, then the data can be rebuilt using the physical
disk on the other side of the mirror.
Figure 3-3. Mirroring Disks
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 the two disks.
• When a disk fails, the virtual disk still works. The data is read from the
failed disk’s mirror.
• 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.