Hp XP P9500 Storage Manuel d'utilisateur télécharger pdf (Page 13)

Note the following regarding performance:

• Host I/O performance (sequential write performance only) to mapped volumes can be improved

by setting SOM 872 to ON. For more information, call the HP Technical Support.

• The performance and status of the external system affect read/write performance of the mapped

external volume. A heavy load on the external system slows the processing speed of read/write

operations. In this case, I/O from a mainframe host may receive a Missing Interrupt error.

• If the host connected to the local storage system issues numerous I/O to be processed by the

external storage system, the commands from the host may time out.

• When you execute HP P9500 software commands that result in more I/O processed than the

external storage system can handle, the commands could time out and an error may occur.

• When you manipulate an external volume from the host, check the Path Blockade Watch time

for the external volume. If the value for this setting is longer than the timeout period of the host

command, the host command may time out when the power supply is off or when an error

occurs in the external storage system. If 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.

Application performance considerations

Performance requirements for an application can be met when using external storage, but note

the following considerations in this regard:

• Internal storage typically provides faster response times than external storage when the storage

is of the same type.

• Storage used by the application must have the proper performance characteristics.

For example, SATA type storage does not provide the performance requirements usually

needed for an OLTP application.

• The mainframe Transaction Processing Facility (TPF) should not use external storage.

Planning external volumes

External volumes must be set up to match External Storage requirements. Note the following:

• You can use pre-existing data in an external volume after it is mapped to the local system,

with the following restrictions:

◦ Emulation type must be set to OPEN-V when you map the volume.

◦ To perform host I/O operations, an LU path from the Target port to the mapped volume

must be set.

• An external volume’s maximum or minimum available capacity depends on the emulation

type you specify when mapping the volume.

See Capacity requirements for volumes (page 16) for more information.

• You cannot access data stored in an external volume beyond the allowed maximum capacity.

See “Maximum capacity of an external volume” in System requirements (page 11).

• You cannot map an external volume whose capacity is smaller than the minimum capacity

required for internal volumes, which is 30 GB.

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Hp XP P9500 Storage Manuel d'utilisateur Page 13