HP XP External Storage Software - Manual (Page 47)

Figure 21 When the External Volume Capacity is Smaller than the Basic Capacity of
Specified Emulation Type
Guidelines for Mainframe Volumes
• If you plan to use the mapped external volume from the mainframe OS (the volume is mapped
with the setting of 3380-x or 3390-x mainframe emulation type), you need to select the external
volume that consists of one LDEV or you need to adjust the capacity of the external volume to
be mapped beforehand. If multiple LDEVs exist in one external volume and if a lot of I/Os are
made to these LDEVs, the read, write commands may become timeout. When the commands
become timeout, the SIM (21D2xx) is reported.
• When you use the mapped external volume from the mainframe OS, set the MIH (Missing
Interrupt Handler) timer to 45 seconds (which is the recommended value).
Volume Attribute Guidelines
• The external volume attributes for all the LDEVs created in an external volume become the same.
The attributes are taken over, when the LDEVs are reconfigured using the VLL function.
• The Cache Mode becomes the same for all the LDEVs in one external volume.
• The attributes that are set for the external volume originally on the external storage system side
(such as the port security, the LUN security, the HP StorageWorks XP Volume Retention Manager
attributes, and so on) are not kept, when the external volume is mapped as an internal volume. If
the original attributes are required to be set, set the attributes on the mapped external volume
from the local storage system side.
• For the external volume, for which the Cache Mode is set to Disable, the bind mode for the Cache
Residency Manager operation is not available.
• If you use the mapped external volume for the Cache Residency Manager operation and set the
bind mode, the cache of twice as much capacity as the user data is required for the Cache
Residency Manager operation.
Creating LUSE Volume Guidelines
• Do not combine LDEVs of multiple external volumes to create a LUSE volume. The LDEVs in the
same external volume can only be used to set the LUSE volumes.
• The mapped volumes that have different cache mode settings cannot be used to create one
LUSE volume.
Maintenance Guidelines for an External Storage System
• Before you change settings of the external storage system, you must delete the external volume
mapping. After you change settings of the external storage system, you must remap the external
volume. If you do not remap the volume, the external volume cannot be used in the local
storage system.
XP24000 External Storage Software User’s Guide 47