Use the following information to calculate the physical and effective capacity of a storage system.
To calculate the total physical capacity of a storage system, multiply each drive-set feature by its total physical capacity and sum the values. For the standard drive enclosures, a full drive-set feature consists of 16 identical disk drives with the same drive type, capacity, and speed. For high-performance flash enclosures, a full drive-set feature consists of 30 identical flash cards.
The logical configuration of your storage affects the effective capacity of the drive set.
Physical capacity can be logically configured as fixed block (FB) or count key data (CKD). Data that is accessed by open systems hosts or Linux on System z® that support Fibre Channel protocol must be logically configured as FB. Data that is accessed by System z hosts with z/OS® or z/VM® must be configured as CKD.
One or more arrays are combined to create a logically contiguous storage space, called a rank. On a multiarray rank, data is striped across the arrays in the rank to improve performance.
Physical capacity for the storage system can be configured as RAID 5, RAID 6, RAID 10, or a combination of RAID 5 and RAID 10. RAID 5 can offer excellent performance for most applications, while RAID 10 can offer better performance for selected applications, in particular, high random, write content applications in the open systems environment. RAID 6 increases data protection by adding an extra layer of parity over the RAID 5 implementation.
Each RAID rank is divided into equal-sized segments that are known as extents. All extents are approximately 1 GB. However, FB extents are slightly larger than CKD extents.