Registering A Volume To An External Volume Group (Exg) - HP StorageWorks XP24000 User Manual

(internal volumes). Identify the volumes in each external storage system that should be mapped as
internal volumes.
You cannot access the data that is stored in an external volume beyond the maximum available
capacity.
For example, if an external volume of 100 GB was mapped as an internal volume of 70 GB,
then 30 GB of the external volume would not be accessible from the local storage system side.
You cannot map an external volume whose capacity is smaller than the minimum available
capacity.
For example, you cannot map an external volume of 10 GB as an internal volume requiring
at least 30 GB.
The maximum or minimum available capacity of an external volume depends on the emulation
type that is set when the volume is mapped. See
Type" (page 147)
number of external volumes that can be mapped, see

Registering a Volume to an External Volume Group (ExG)

When you map an external volume as an internal volume, you need to register the external volume
to an external volume group.
External volumes, which are set by XP External Storage, can be classified into groups by usage.
Any group of this type is called an external volume group (ExG). For instance, you can register
multiple volumes in one external storage system to one external volume group. Or you can register
the volumes in one external volume group and manage them in block, even though the data you
want to manage in a lump is stored in volumes in the different external storage systems.
You need to assign numbers to external volume groups. See
(page 36) for details on a maximum number of external volume groups, or a maximum number of
volumes to be registered in one external volume group.
Configuring External Volume Attributes
When you map an external volume as an internal volume, you set the attributes of the external
volume. External volume attributes can be set using the mapping policy or the Set External Volume
Parameter dialog box of XP External Storage. For details on the mapping policy, see
Mapping Policy" (page
"Set External Volume Parameter Dialog Box" (page
The attributes of the external volume are as follows:
Emulation type
Select an emulation type for the mapped external volume from the list.
The emulation type OPEN-V must be selected if, after the mapping, you are planning to use
the existing data in the external volume from the local storage system. For example, to migrate
the existing data in the external volume to the local storage system volume, set the OPEN-V
emulation type when the external volume is mapped.
If you select the emulation type other than OPEN-V, the volume requires a specific area to be
provided for management data. Once this area is provided, volume capacity after the mapping
becomes less than the actual external volume capacity for the area (volume). For details on
volume capacity, see
Cache Mode (Enable or Disable)
Cache mode specifies whether the write data from the host to the external storage system is
propagated synchronously (Disable) or asynchronously (Enable). By default, cache mode is
16 About XP External Storage Operations
for the capacity of the external volume for each emulation type. For the maximum
25). For details on the Set External Volume Parameter dialog box, see
"Capacity Guidelines" (page
"Required Volume Capacity for Each Emulation
"XP External Storage Requirements" (page
"XP External Storage Requirements"
68).
39).
36).
"Choosing
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