HP XP External Storage Software - Manual (Page 48)

The examples of external storage system settings which require the re-mapping of external volume
are as follows:
• Changing WWNs of target ports which connect to the local storage system
• Changing the serial number of the external storage system
• Changing LUNs of volumes of the external storage system
• Reducing the volume capacity of the external storage system so that the volume capacity is
smaller than when volume mapping was performed
Besides, re-mapping is required for External Storage after you change external storage system
settings that require modification on the host side when hosts are connected directly to a external
storage system.
Before you delete the external volume mapping, make sure that the volume has no
LU paths, and that the volume is not a component of any pairs (such as Continuous
Access pairs). For detailed information on deleting the external volume mapping, see
“ Deleting the External Volume Mapping ” on page 96. For detailed information on mapping
external volume, see “ Mapping an External Volume Automatically ” on page 69.
Performance and Status Guidelines
• The performance and status of the external storage system affect the Read and Write performance
of the mapped external volume. If there is a heavy load on the external storage system, the
processing speed of the Read and Write operation becomes slow. In this case, the I/Os from
the mainframe host may become MIH error.
• If the host connected to the local storage system issues too many I/Os to be processed by the
external storage system, the commands from the host may possibly be timed out.
When the amount of I/Os from the host to the external volume exceeds the maximum amount of
I/Os that the external storage system can accept, the commands from the host to the local storage
system may possibly be timed out. As you configure the system using the external volumes,
consider the capability for the I/O amount of the external storage system.
• When you execute the commands of the storage system program products to the mapped external
volume and thus too many I/Os are issued to be processed by the external storage system, the
commands may possibly be timed out and an error may occur.
When the amount of I/Os from the program products to the external volume exceeds the maximum
amount of I/Os that the external storage system can accept, the commands from the program
products may possibly be timed out and an error may occur. As you configure the system using
the external volumes, consider the capability for the I/O amount of the external storage system.
• When you use an external volume from the host, note the Path Blockade Watch time for the
external volume. If the Path Blockade Watch time is longer than the timeout period of the host
command, the commands from the host may possibly be timed out when the power supply is off
or when an error occurs for the external storage system. If the host I/O is a significant concern,
make sure that the Path Blockade Watch time of the external volume is the same as or shorter
than the timeout period of the host command.
RAID Level Considerations
In the internal processing, the RAID level of the external volume is handled as RAID-1 across the board.
The bar (−) is displayed on the Remote Web Console windows. The RAID level of external volumes is
reported as RAID-1 when information about external storage system is reported to the higher-level device
(OS).
Installing and Uninstalling External Storage
This section explains how to install and uninstall External Storage.
48 Preparing for External Storage Operations