Functional and Operational Characteristics
2–49
Hitachi VSP User and Reference Guide
900 Volume
Migration
In combination with SOM899 setting, whether to
execute and when to start the I/O synchronous
copy change as follows.
Mode 900 = ON:
SOM899 is ON: I/O synchronous copy starts when
the threshold of Volume Migration retry is
exceeded.
SOM899 is OFF: I/O synchronous copy starts when
the number of retries reaches half of the threshold
of Volume Migration retry.
Mode 900 = OFF (default):
SOM899 is ON: I/O synchronous copy starts when
the threshold of Volume Migration retry is
exceeded. (Recommended)
SOM899 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
901 Dynamic
Tiering
Dynamic
Tiering for
Mainframe
By setting the mode to ON or OFF, the page
allocation method of Tier Level ALL when the drive
type of tier1 is SSD changes as follows.
Mode 901 = ON:
For tier1 (drive type is SSD), pages are allocated
until the capacity reaches the limit. Without
consideration of performance limitation
exceedance, allocation is done from highly loaded
pages until reaching the capacity limit
When the capacity of the tier1 reaches the
threshold value, the minimum value of the tier
range is set to the starting value of the lower IOPH
zone, and the maximum value of the lower tier
range is set to the boundary value.
Mode 901 = OFF (default):
For tier1 (drive type is SSD), page allocation is
performed based on performance potential
limitation. With consideration of performance
limitation exceedance, allocation is done from
highly loaded pages but at the point when the
performance limitation is reached, pages are not
allocated any more even there is free space.
When the capacity of the tier1 reaches the
threshold value, the minimum value of the tier
range is set to the boundary value, and the
maximum value of the lower tier range is set to a
value of boundary value x 110% + 5 [IOPH].
OFF
Mode Category Description Default MCU/RCU
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