HP StorageWorks External Storage XP user guide (T1706-96006, June 2006)

External Storage XP user guide 141
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.
According to these restrictions, you can determine the external LU’s maximum usable capacity for each
emulation type. When the mapped external LU’s capacity is more than the maximum capacity of the
specified emulation type, a certain part of the external LU cannot be used.
Table 25 External LU’s maximum usable capacity
Emulation type External LU’s maximum usable capacity
OPEN-V 2 TB
OPEN emulation type other than OPEN-V 575.98 GB
3380 mainframe emulation type 575.98 GB
3390 mainframe emulation type 695.98 GB