Virtual LUN size calculations

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 Hitachi Device Manager - Storage Navigator.