HP Surestore Disk Array FC60 HP SureStore E Disk Array FC60 Service Manual (A5 - Page 62

Capacity Management Features The disk array uses a number of features to manage its disk capacity efficiently. Volume groups allow you to partition the total disk capacity into smaller, functional entities. Caching improves disk array performance by using controller RAM to temporarily store data during I/Os. Volume Groups The capacity of the disk array can be divided into entities called volume groups. Individual disks are grouped together to form a volume group. Functionally, each volume group appears to the host operating system as an individual disk drive. Although the volume group appears to the host as an individual disk, the use of multiple disks offers advantages of increased data availability and performance. Data availability is enhanced by using redundant data stored on a separate disk from the original data. The use of multiple disks increases performance by allowing simultaneous access to several disks when reading and writing data. Disk Groups A disk group is a collection of individual disks that share a common role in disk array operation. All disks on the disk array become a member of one of the following disk groups: • Volume group - Each volume group on the disk array has its own disk group. When a disk is included as part of a newly created volume group, the disk becomes a member of the associated disk group. • Hot spare group - All disks assigned the role of global hot spare become members of this group. Up to six disks (one for each channel) can be assigned as global hot spares. • Unassigned group - Any disk that is neither part of a volume group nor a global hot spare is considered unassigned and becomes a member of this group. Unassigned disks can be used to create a volume group or can be used as global hot spares. Unassigned disks do not contribute to the capacity of the disk array. 62 Capacity Management Features