One or more arrays are combined to create a logically contiguous
storage space called a rank.
On a multi-array rank, data is striped (RAID 0) across the arrays in the
rank to improve performance. The available space on each rank will be divided
into extents. The extents are the building blocks of the logical volumes.
An extent is striped across all disks of an array. The process of forming
a rank does two things:
- The array is defined for either fixed block (open systems) or CKD (zSeries)
data. This determines the size of the set of data contained on one disk within
a stripe on the array.
- The capacity of the array is subdivided into equal sized partitions, called
extents. The extent size depends on the extent type, FB or CKD.