HP Surestore Disk Array FC60 HP SureStore E Disk Array FC60 Service Manual (A5 - Page 45

Product Description 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. Although RAID 0 is supported, 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. Disk Array High Availability Features 45