User guide

System option modes B–25
Hitachi Unified Storage VM Block Module Hardware User Guide
900 Volume
Migration
In combination with the SOM8 99 setting, whether to
execute and when to start the I/O synchronous copy
change as follows.
Mode 900= ON:
SOM 899 is ON: I/O synchronous copy starts without
retrying Volume Migration.
SOM900 is OFF: I/O synchronous copy starts when the
threshold of Volume Migration retry is exceeded.
(Recommended)
Mode 899 = OFF (default):
SOM900 is ON: I/O synchronous copy starts when the
number of retries reaches half of the threshold of Volume
Migration retry.
SOM900 is OFF: Volume Migration is retired and I/O
synchronous copy is not executed.
Note:
1. This mode is applied when improvement of Volume
Migration success rate is desired under the condition that
there are many updates to a migration source volume of
Volume Migration.
2. During I/O synchronous copy, host I/O performance
degrades.
OFF .
Mode Category Description Default
MCU/
RCU