Hitachi Virtual Storage Platform G400, Reference Manual

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See the System Option Mode 729 and 803 sheet for more
details.
Notes:
1. This mode is applied when
- a file system using DP pool VOLs is used.
- Data Retention Utility is installed.
2. Because the DRU attribute is set to Protect for the V-VOL,
a read I/O is also disabled.
3. If Data Retention Utility is not installed, the expected
effect cannot be achieved.
4. The Protect attribute of DRU for the HDP V-VOL can be
released on the Data Retention window of Storage Navigator
after recovering the blocked pool VOL.
5. With HM800 V01+1 and later, do not change the mode
setting but use the virtual volume protection function when
the pool volume is blocked to change the setting.
855
By switching the mode to ON/OFF when ShadowImage is
used with System Option Mode 467 set to ON, copy
processing is continued or stopped as follows.
Mode 855 = ON:
When the amount of dirty data is within the range from
58% to 63%, the next copy processing is continued after
the dirty data created in the previous copy is cleared to
prevent the amount of dirty data from increasing (copy after
destaging). If the amount of dirty data exceeds 63%, the
copy processing is stopped.
Mode 855 = OFF:
The copy processing is stopped when the amount of dirty
data is over 60%.
For details, see the System Option Mode 855 sheet.
Notes:
1. This mode is applied when all the following conditions are
met.
- ShadowImage is used with System Option Mode 467 set to
ON.
- Write pending rate of an MP blade that has LDEV
ownership of the copy target is high.
- Usage rate of a parity group to which the copy target
LDEV belongs is low.
- ShadowImage copy progress is delayed.
2. This mode is available only when System Option Mode
467 is set to ON.
OFF
System option modes 69
Hitachi Virtual Storage Platform G400, G600 Hardware Reference Guide