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Chapter 3 Storage Arrays 3-59
RAID
1
Striping/
Mirroring
Mode
• Also called RAID 10 or 0+1.
• A minimum of two drives is required for RAID 1;one for the
user data and one for the mirrored data.
• Offers the best availability high performance and the best
data availability. Data is written to two duplicate disks
simultaneously. If one of the disk drives in a disk-pair fails,
the system can instantly switch to the other disk without
any loss of data or service. However, only half of the drives
in the volume group are available for user data.
• Uses disk mirroring to make an exact copy from one drive
to another drive.
• A single drive failure causes associated volumes become
degraded, but the mirror drive allows access to the data.
• Can survive multiple drive failures as long as no more than
one failure exists per mirrored pair.
• A drive-pair failure in a volume group causes all associated
volumes to fail and data loss could occur.
RAID
3
High
Bandwidth
Mode
• Both user data and redundancy data (parity) are striped
across the drives.
• The equivalent of one drive's capacity is used for
redundancy data.
• Good for large data transfers in applications such as
multimedia or medical imaging that write and read large
sequential chunks of data.
• A single drive failure in a volume group causes associated
volumes to become degraded, but the redundancy data
allows access to the data.
• Two or more drive failures in a volume group cause all
associated volumes to fail and data loss could occur.
RAID
5
High I/O Mode • Both user data and redundancy data (parity) are striped
across the drives.
• The equivalent of one drive's capacity is used for
redundancy data.
• Good for multi-user environments such as database or file
system storage, where typical input/output (I/O) size is
small and there is a high proportion of read activity.
• A single drive failure in a volume group causes associated
volumes to become degraded, but the redundancy data
allows access to the data.
• Two or more drive failures in a volume group causes all
associated volumes to fail and data loss could occur.
TABLE 3-9 RAID Level Configurations
RAID
Level Short Description Detailed Description