HP Surestore Disk Array FC60 HP SureStore E Disk Array FC60 Service Manual (A5 - Page 397

frame The smallest indivisible unit of application-data transfer used by Fibre Channel. Frame size depends on the hardware implementation and is independent of the application software. Frames begin with a 4-byte Start of Frame (SOF), end with a 4-byte End of Frame (EOF), include a 24-byte frame header and 4-byte Cyclic Redundancy Check (CRC), and can carry a variable data payload from 0 to 2112 bytes, the first 64 of which can be used for optional headers. FRU (Field Replaceable Unit) A disk array hardware component that can be removed and replaced by a customer or Hewlett-Packard service representative. global hot spare A disk that is powered up and electrically connected to a disk array but not used until a disk failure occurs. A global hot spare is a dedicated, on-line, backup disk that cannot be used to store user data during normal disk array operation. If any disk in a LUN fails, the disk array automatically begins rebuilding the failed disk's content on an available global hot spare. When the rebuild process completes, the LUN functions normally, using the global hot spare as a replacement for the failed disk. Up to six disks (one for each channel) can be assigned as global hot spares. hardware path See primary disk array path. HBA See adapter. high availability The technique of designing systems that remain operational even if a hardware or other type of failure occurs. The disk array achieves high availability by using redundant data and global hot spare disks to maintain access to user data in the event of a disk failure. Redundant hardware assemblies also ensure high availability in the event of a failure. 397 Glossary