Hitachi AMS 2100 Hardware Manual page 227

NOTE: The response performance mode is enabled only when the
segment size is 16 kB or less. Be careful when using it with Cache Partition
Manager.
If you attempt to change the mode from response performance mode to
the normal mode while the I/O load is heavy, the setting may not change
and an error message is displayed. If this happens, follow the instructions
in the error message, wait until after the host I/O stops, and change the
setting again.
The processor speed becomes high while operating in the response
performance mode compared to the rate in the normal mode. During this
time, it may not be possible to upgrade the firmware. Hitachi Data Systems
recommends that if you cannot upgrade the firmware while operating in the
response performance mode, change the mode to normal and then upgrade
the firmware.
If the mode setting is successful, a confirmation message is displayed. Click
Close to exit the message box and return to the Tuning Parameters window,
where you can confirm that the setting has changed.
Multi-Stream configuration
Use the Multi Stream window to configure certain parameters that change
the multi-stream scope, initialize parameter settings, and edit multi-stream
options.
To display or set the multi-stream:
Hitachi AMS 2100/2300 Storage System Hardware Guide
Configuration
7–45