HP XP External Storage Software - Manual (Page 46)

When the amount of I/Os from the host to the external LU exceeds the maximum amount of I/Os
the external array can accept, commands from the host to the local array might time out. As you
configure the system using external LUs, consider the external array's I/O capacity.
• When executing commands in HP StorageWorks software products to the mapped external LU
and, therefore, too many I/Os are issued for the external array to process, commands might time
out and errors might occur.
When the amount of I/Os from the software products to the external LU exceeds the maximum
amount of I/Os the external array can accept, commands might time out and errors might occur.
As you configure the system using external LUs, consider the external array's I/O capacity.
• When using an external LU from the host, note the external LU's Path Blockade Watch time. If the
Path Blockade Watch time is longer than the host command's timeout period, commands from the
host might time out when the power supply is off or errors occur for the external array. If host I/O
is a significant concern, ensure that the external LU's Path Blockade Watch time is the same as or
shorter than the host command's timeout period.
• Host access to the external storage LU must be via the local array, and must not be via a direct
physical connection to the external storage device LU. For external array LUs not involved with
External Storage XP, direct access from a host is allowed for all supported external storage except
MSA. If you use MSA as external storage, it must be entirely dedicate as external storage.
• For all external storage, either set the ES XP cache mode option in Command View XP or XP Remote
Web Console to cache disabled or partition resources associated with external storage in its own
CLPR (for example, CLPR1). While HP strongly recommends this new default for all external storage
in general, this new default is mandatory for any external array that is slower than an XP12000
external port (for example, the Modular Smart Array product line) unless it resides in its own CLPR
partition with isolated port/MP/cache resources.
Combining External Storage XP with other HP StorageWorks
products
You can use HP StorageWorks software products to operate and manage the external LUs you set
using External Storage XP.
The following sections provide configuration examples for specific HP StorageWorks software products:
• Using external LUs for Auto LUN XP operations
• Using external LUs for Continuous Access XP operations
• Using external LUs for Continuous Access XP Journal operations
• Using external LUs for Business Copy XP operations
• Using external LUs for Snapshot XP operations
The following HP StorageWorks software products support the use of mapped external LUs. For
operations and notes about each software product, see the product's user guide.
• LUN Manager
• If you set an open-system emulation type when mapping the external LU, you must use LUN
Manager to set the mapped LU's path.
• You cannot use the mapped external LU as a NAS system volume.
• You cannot use the mapped external LU as a NAS user volume.
• Volume Manager
• If you set a mainframe-system emulation type when mapping the external LU, you must format
the mapped volume or perform the Write to Control Blocks operation using the Custom Volume
Size (CVS) function before putting the external LU into use. For instructions, see the
Preparing for External Storage XP operations 46