HP XP External Storage Software - Manual (Page 183)

B Required volume capacity for emulation
types
When mapping an external LU as a local array internal LDEV, you must specify the mapped volume's
emulation type.
The capacity required for the LDEV to be mapped is the total capacity of the data area for storing
actual user data and the control information area for storing control information. The capacity of the
data area (called base data area capacity) and the capacity of the control information area (called
control information area capacity) depend on the emulation type. The minimum capacity of the data
area for Customized Volume (CV) (called minimum data area capacity) also depends on the emulation
type.
Use the following equation to calculate the minimum capacity required for an LDEV (minimum LDEV
capacity) for each emulation type:
Minimum LDEV capacity = Minimum data area capacity + control information area capacity
If the external LU's capacity is less than this minimum LDEV capacity, the emulation type cannot be
specified.
Use the following equation to calculate the base LDEV capacity for each emulation type:
Base LDEV capacity = Base data area capacity + Control information area capacity
When the external LU's capacity is less than the emulation type's base LDEV capacity, one CV is
created in the external LU as you map the volume. When the external LU's capacity is more than the
emulation type's base LDEV capacity, the external LU is divided into multiple LDEVs, each having the
base LDEV capacity. Because the OPEN-V emulation type supports a maximum of 2TB of the volume,
one LDEV is always created when the external LU is mapped.
If you use Volume Manager, you can divide the mapped external LU into a maximum of 256 CVs.
However, LDEVs as they are mapped are used for the OPEN-L emulation type because Volume
Manager is not applicable to the OPEN-L emulation type.
The following restrictions apply for the external LU's maximum usable capacity:
• The external LU can be divided into a maximum of 256 CVs. Therefore, the external LU's maximum
capacity must meet the following equation:
Maximum usable capacity of the external LU Base LDEV capacity × 256
• Each emulation type has its own maximum usable capacity. Table 25 shows the external LU's
maximum usable capacity for each emulation type.
Table 25 External LU's maximum usable capacity
External LU's maximum usable capacity Emulation type
2 TB OPEN-V
575.98 GB OPEN emulation type other than OPEN-V
575.98 GB 3380 mainframe emulation type
External Storage XP user guide for the XP12000, XP10000, SVS200 183