HP Surestore Disk Array 12h and FC60 - Manual (Page 47)

Disk Array High Availability Features 47
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Disk Array High Availability Features
High availability systems are designed to provide uninterrupted operation should a
hardware failure occur. Disk arrays contribute to high availability by ensuring that user
data remains accessible even when a disk or other component within the Disk Array FC60
fails. Selecting the proper Fibre Channel topology and system configuration can protect
against the failure of any hardware component in the I/O path to the disk array by providing
an alternate path to all user data.
The Disk Array FC60 provides high availability in the following ways:
• Supported RAID levels 1, 0/1, 3, and 5 all use data redundancy to protect data when a disk
failure occurs. RAID 0 is supported but it does not offer data redundancy and should not
be used in high-availability environments.
• Global hot spare disks serve as automatic replacements for failed disks.
• Alternate hardware paths to user data protects against I/O path failures.
• Redundant, hot-swappable hardware components can be replaced without interrupting
disk array operation.
RAID Technology
RAID technology contributes to high availability through the use of data redundancy,
which ensures that data on the disk array remains available even if a disk or channel failure
occurs. RAID technology uses two techniques to achieve data redundancy: mirroring and
parity. A third characteristic of RAID technology, data striping, enhances I/O performance.
Disk Mirroring
Disk mirroring achieves data redundancy by maintaining a duplicate copy of all data. Disks
are organized into pairs: one disk serves as the data disk, the other as the mirror which
contains an exact image of its data. If either disk in the pair fails or becomes inaccessible,
the remaining disk provides uninterrupted access to the data.