HP XP External Storage Software - Manual (Page 41)

• If you map an external LU that is equal to or greater than 695.98 GB with a 3390 mainframe
emulation type, you can access data stored in the field up to 695.98 GB. You cannot access data
stored in the field over 695.98 GB.
However, for emulation types with a small base capacity, some of the field of 695.98 GB might
not be available. For more information, see
Required volume capacity for emulation types .
• If you plan to use the mapped external LU from the mainframe OS (volume is mapped with a
3380-x or 3390-x mainframe emulation type), you must select an external LU that consists of one
LDEV or you must first adjust the capacity of the external LU to be mapped. If multiple LDEVs exist
in one external LU and if numerous I/Os are made to these LDEVs, the read and write commands
might timeout. When the commands timeout, the SIM (21D2xx) is reported.
• When mapping an external LU as internal LDEVs with emulation types other than OPEN-V, the
number of volumes and the volume capacity of the mapped internal LDEVs depends on the original
external LU's capacity and each emulation type's normal size. When mapping an external LU
using emulation types other than OPEN-V, an XP array management information area is required
in the mapped LU. This means that the capacity available after mapping is slightly smaller than
the actual external LU capacity. Available capacity decreases by the size of the XP array
management information area, and all prior data must be considered lost. For more information,
see the HP StorageWorks Flex Copy XP user guide.
Figure 12 shows an example where the external LU's original capacity is larger than (or a multiple
of) the normal size of the local array's emulation type (OPEN-3 in this example). Therefore, in this
example, the local array can realize two fully-sized OPEN-3 LDEVs, with some space (insufficient
to create a full OPEN-3) left over.
Figure 12 Ext. LU cap. is larger than the spec. emulation type's basic cap. (OPEN-3 ex.)
Figure 13 shows an example where the external LU's original capacity is smaller than the normal
size of the local array's emulation type. In this example, since the resulting space is insufficient to
create a local array OPEN-3 LDEV, you can designate it as either a local array OPEN-V or an
OPEN-3 CVS LDEV. If the external LU were an XP of OPEN-3 emulation type, forfeiting a small
amount of management space would also result in an OPEN-3 CVS volume or an OPEN-V.
External Storage XP user guide for the XP12000, XP10000, SVS200 41