Hp XP P9500 Storage User Manual download pdf (Page 15)

Enabled can adversely impact overall HP P9500 performance if the I/O rate exceeds the

performance capabilities of the external system. If you specify Enabled, you should use the same

formula for sizing cache in both the internal and external systems.

A cache partition should be defined when Enabled is used for the Cache Mode setting. A CLPR

helps to protect overall HP P9500 performance when the I/O rate tends to exceed the capabilities

of the external system.

Cache Mode effects with other HP software

Note the following additional effects regarding the Cache Mode setting:

• If you perform the Cache Residency bind mode operation on an external volume, Cache Mode

is set to Enabled. In this case, twice as much cache capacity as user data area capacity is

required for the operation. (Bind mode is unavailable when Ext Stor Cache Mode is set to

Disable.)

• The external volumes in a LUSE must all use the same Cache Mode setting, either Enabled or

Disabled.

• The external volumes in a Thin Provisioning pool must all use the same Cache Mode setting,

either Enabled or Disabled.

• Smart Tiers pool volumes require Cache Mode to be set to Enabled.

• Data that is not written by the host (for example, data written by Business Copy) is

asynchronously destaged to the external storage system regardless of the Cache Mode setting.

• When you set emulation type for a mainframe system, note the following:

Data written by a host using a Format Write command is asynchronously destaged to the

external storage system regardless of the Cache Mode setting.

◦

◦ Data written by a host using other Write commands are destaged to the external storage

system as configured in the Cache Mode setting.

Mainframe volumes

Note the following requirements and considerations for mapping mainframe external volumes:

• Make sure that mainframe external volumes on a mainframe operating system consist of at

least one LDEV before mapping.

• When multiple LDEVs exist in an external volume and numerous I/Os are made to them,

read/write commands may timeout. When the commands timeout, the SIM (21D2xx) is

reported.

• Set the MIH (missing interrupt handler) timer to 45 seconds (which is the recommended value)

for mainframe external volumes on a mainframe operating system.

• Pre-existing mainframe volumes on an external system that are accessed by FICON channels

cannot be mapped to the local storage system because the HP P9500 does not recognize

these volumes

You can prepare mainframe external volumes for mapping using one of the following methods:

◦ Zero-format the external volumes on the external system, map the volumes to the HP

P9500, then perform the Write to Control Blocks operation using Virtual LVI/Virtual LUN

on the local system side.

◦ Map the external volumes to the HP P9500, and then format the mapped volumes on the

local storage system using the Virtual LVI/Virtual LUN.

Planning external volumes 15

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Hp XP P9500 Storage User Manual Page 15

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