HP StorageWorks XP Remote Web Console Software - Manual (Page 24)

maximum of 8,192 external LU groups. You can register a maximum of 256 volumes in one external
group.
External LU attributes set by mapping
When mapping an external LU as an internal LDEV, use the Add LU pane in XP External Storage to
set the external LU's attributes. For instructions, see
Mapping external LUs (Add LU) .
The following are the external LU's attributes:
• Emulation type
Set the mapped LU's emulation type by selecting any emulation type from the drop-down list.
However, if you plan to use the mapped LU for XP Flex Copy operations, or you plan to access
existing data in the external LU, you must select the OPEN-V emulation type to avoid data resizing.
If you plan to use existing data in the external LU from the local array after mapping, you must
select the OPEN-V emulation type. For example, to migrate existing data in the external LU to the
local array volume, you must set the OPEN-V emulation type when mapping the external LU.
You must also select the OPEN-V emulation type when VMA of HP StorageWorks XP LUN Security
Extension Software is set for the external LU on the external array side.
If you select an emulation type other than OPEN-V, additional space is taken for XP management
information. This means that after mapping, LU capacity is less than the actual external LU capacity
(and the original data must be considered lost). For more information about volume capacity, see
Limitations on External Storage XP operations .
• IO Suppression mode (Enable or Disable)
When mapping an LU, determine whether to suppress I/O operations from hosts (via the local
array) to the mapped external LU.
If you select Enable, you can use the mapped LU only for XP Flex Copy operations.
If you select Disable, a host connected to the local array can use the mapped external LU as if it
were an LU inside the local array, but you cannot use the LU for XP Flex Copy operations.
You can select Enable only when you set the OPEN-V emulation type for the mapped LU. When
you set an emulation type other than OPEN-V, the IO Suppression mode is automatically set to
Disable.
• Cache Mode (Enable or Disable)
Cache mode specifies if I/O from the host is propagated synchronously (Disable) or asynchronously
(Enable) to the external storage device. By default cache mode is set to Enable. All I/O to and
from the local array in both cache modes always uses cache. Write operations are always backed
up in duplex cache.
If you select Enable, the local array signals the host that an I/O operation completed after receiving
the data into the local array's cache memory, and then asynchronously destages the data to the
external array.
If you select Disable, the local array signals the host that an I/O operation completed only after
the local array has synchronously written the data to the external array.
When IO Suppression mode is set to Enable, Cache Mode changes by default to Disable.
If you use an external LU and set Cache Mode to Disable for HP StorageWorks XP Cache LUN
Software operations, you cannot use the XP Cache LUN Bind mode. For more information, see
the HP StorageWorks XP Cache LUN user guide for XP12000/XP10000 Disk Arrays and SVS
200.
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