When creating a CV, you can specify the capacity of each CV. However, rounding will produce different values for the user-specified CV capacity and the actual entire CV capacity. To estimate the actual capacity of a CV, use a mathematical formula. The following topics explain how to calculate the user area capacity and the entire capacity of a CV.

The capacity of a CV or an LDEV consists of two types of capacity. One type is the user area capacity that stores the user data. The second type is the capacities of all areas that are necessary for an LDEV implementation including control information. The sum of these two types of capacities is called the entire capacity.

Implemented LDEVs consume the entire capacity from the parity group capacity. Therefore, even if the sum of user areas of multiple CVs and the user area of one CV are the same size, the remaining free space generated when multiple CVs are created may be smaller than the free space in the parity group when one CV is created.

When using CCI, the specified size of CVs is created regardless of the capacity calculation. Therefore, even if the same capacity size (for example, 1 TB) appears, the actual capacity size might be different between the CVs created by CCI and the CVs created by Device Manager - Storage Navigator.

When you create an LDEV using the Create LDEVs window, depending on the Capacity Compatibility Mode (Offset boundary) option, the capacity of LDEV differs even if the specified value is the same. If the Capacity Compatibility Mode (Offset boundary) option is selected, the specified LDEV capacity is offset by conforming to the prescribed boundary values, and an LDEV is created. For details about the prescribed boundary values, see Calculating fixed-size volume size (CV capacity unit is MB), Calculating fixed-size volume size (CV capacity unit is blocks), Calculating volume size (CV capacity unit is MB), or Calculating volume size (CV capacity unit is blocks).

If the Capacity Compatibility Mode (Offset boundary) option is not selected, the capacity of the LDEV is created with the specified size. In the storage system, data is managed based on a slot, and the data protection is performed based on a parity stripe unit. For an LDEV with capacity offset by a boundary, the efficiency of the drive capacity is improved because the capacity of LDEV is offset by the unit of the data management. If you want to create copy pairs with VSP, HUS VM, or previous storage system, exactly the same LDEV capacity must be used for the volumes in a pair. If there is an emphasis on the efficiency of the drive capacity, select the Capacity Compatibility Mode (Offset boundary) option when creating LDEVs. If you want the LDEV capacity to be a specific size, do not select the Capacity Compatibility Mode (Offset boundary) option when creating LDEVs.