HP StorageWorks External Storage XP user guide (December 2005)

External Storage XP user guide 27
example, the XP10000/XP12000 can realize two fully-sized OPEN-3 LDEVs, with some space
(insufficient to create a full Open-3) left over.
Figure 14 External LU capacity is larger than capacity of specified emulation type
• Figure 15 shows an example where the original capacity of the external LU is smaller than the normal
size of the XP10000/XP12000 emulation type. In this example, since the resulting space is insufficient
to create an XP10000/XP12000 OPEN-3 LDEV, you can designate it as either an
XP10000/XP12000 OPEN-V or as an “OPEN-3 CVS” LDEV. If the external LU were an XP of OPEN-3
emulation type, the forfeiting of a small amount of management space would also result in either an
“OPEN-3 CVS,” XP10000/XP12000 volume, or an OPEN-V.
Figure 15 External LU capacity is smaller than basic capacity of specified emulation type
IO Suppression mode and Cache Mode
• IO Suppression mode can only be set to Enable when OPEN-V emulation is set for the volume being
mapped. If a different emulation type is set, IO Suppression mode is set automatically to Disable.
• When accessing a mapped external LU from a host connected to the local disk array, set the IO
Suppression mode to Disable. For External Storage XP, select Disable. For Flex Copy XP, select Enable.
• The local disk array does not force the external disk array to reserve the mapped external LU. Therefore,
do not write directly to an external disk array LU with IO Suppression mode set to Disable.
• IO Suppression mode and Cache Mode are set automatically to the same status for all LDEVs in a given
external LU.
Attributes
• External LU attributes (emulation type, IO Suppression mode, and Cache Mode) set when the LU is
mapped cannot be changed while the LU is mapped. To change these attributes, delete the external LU
mapping (Delete LU operation), and remap the LU with different attributes (Add LU operation).
• External LU attributes for all LDEVs created in an external LU are set to the same values. Those attributes
are modified when the LDEVs are reconfigured using Volume Management.