* For the information of operating conditions, refer to
Provisioning Guide for Open Systems.
Mode 896 = ON:
The background format function is disabled.
Mode 896 = OFF:
The background format function is enabled.
Notes:
1. <HUS VM> The mode is applied when a customer
requires disabling the background format for a DP/DT/TI*1
pool due to a concern of performance degradation of other
functions in an environment where a DP-VOL is used by
other functions.
2. When the background format function is enabled,
because up to 42MB/s of ECCG performance is used, local
copy performance may degrade by about 10%. Therefore,
confirm whether the 10% performance degradation is
acceptable or not before enabling the function.
3. When a Dynamic Provisioning VOL on an external storage
system, which is used as an external VOL, is used as a pool
VOL, if the external pool on the external storage side
becomes full due to the background format, the external
VOL may be blocked.
If the external pool capacity is smaller than the external
VOL capacity (Dynamic Provisioning VOL of external storage
system), do not enable the background format function.
4. If the background format function is disabled by changing
the mode setting, the format progress is initialized and the
entire area become unformated.
897
By the combination of System Option Mode 897 and 898
setting, the expansion width of Tier Range upper I/O value
(IOPH) can be changed as follows.
Mode 897 = ON:
System Option Mode 898 is OFF: 110%+0IO
System Option Mode 898 is ON: 110%+2IO
Mode 897 = OFF (Default)
System Option Mode 898 is OFF: 110%+5IO (Default)
System Option Mode 898 is ON: 110%+1IO
By setting the System Option Modes 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.
OFF
System option modes 75
Hitachi Virtual Storage Platform G800 Hardware Reference Guide
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