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Installing and uninstalling external storage, Performance and status guidelines, Raid level considerations – HP XP External Storage Software User Manual

Page 48

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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

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