Hitachi VSP User and Reference Guide
2–48
Functional and Operational Characteristics
898 Dynamic
Tiering,
Dynamic
Tiering for
Mainframe
I/O value (IOPH) can be changed as follows.
Mode 898 = ON:
SOM 897 is OFF: 110%+1IO
SOM 897 is ON: 110%+2IO
Mode 898 = OFF (default):
SOM 897 is OFF: 110%+5IO (Default)
SOM 897 is ON: 110%+0IO
By setting the SOM s to ON to lower the upper limit
for each tier, the gray zone between other tiers
becomes narrow and the frequency of page
allocation increases.
Notes:
1. Apply the mode when the usage of upper tier is
low and that of lower tier is high.
2. The mode must be used with SOM 897.
3. Narrowing the gray zone increases the number
of pages to migrate between tiers per
relocation.
4. When Tier1 is SSD while SOM 901 is set to ON,
the effect of SOM 897 and 898 to the gray zone
of Tire1 and Tier2 is disabled and the SOM 901
setting is enabled instead. In addition, the
settings of SOM 897 and 898 are effective for
Tire2 and Tier3.
Please also see spreadsheet "SOM 897_898_901"
for more details about the relations between SOM
897, 898 and 901.
OFF ..
899 Volume
Migration
In combination with the SOM 900 setting, whether
to execute and when to start the I/O synchronous
copy change as follows.
Mode 899 = ON:
SOM 900 is ON: I/O synchronous copy starts
without retrying Volume Migration.
SOM 900 is OFF: I/O synchronous copy starts
when the threshold of Volume Migration retry is
exceeded. (Recommended)
Mode 899 = OFF (default):
SOM 900 is ON: I/O synchronous copy starts when
the number of retries reaches half of the threshold
of Volume Migration retry.
SOM 900 is OFF: Volume Migration is retired and I/
O synchronous copy is not executed.
Notes:
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
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