Hitachi VSP G200 System Administration Manual page 369

Mode Category
855 ShadowImage
Volume Migration
857 Common
System Administrator Guide for VSP Gx00 models and VSP Fx00 models
Description
For more details, contact customer support (see SOM729 &
803 sheet).
Notes:
1. This SOM 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 DP V-VOL can be
released on the Data Retention window of Device
Manager - Storage Navigator after recovering the
blocked pool VOL.
5. With 83-01-21-x0/00 and later, the Virtual Volume
Protection (VVP) function is supported. VVP can be
enabled/disabled for each pool. With SOM 803 disabled,
VVP is also disabled by default, but you can enable VVP
for each pool as needed. With SOM 803 enabled, VVP is
also enabled automatically (by default) when you create
a new pool. Caution: A pool is NOT protected by ANY
FUNCTION if you deliberately turn VVP for the pool from
ON (default) to OFF, even with SOM 803 enabled.
By switching this SOM to ON/OFF when ShadowImage is used
with SOM 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 (default): The copy processing is stopped
when the amount of dirty data is over 60%.
For details, contact customer support (see SOM855 sheet).
Notes:
1. This SOM is applied when all the following conditions
are met
• ShadowImage is used with SOM 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 SOM is available only when SOM 467 is set to ON.
3. If the workload of the copy target parity group is high,
the copy processing may not be improved even if this
SOM is set to ON.
This SOM enables or disables to limit the cache allocation
capacity per MP blade/unit to within the prescribed capacity*
except for Cache Residency Manager.
System option modes
Default MCU/RCU
OFF -
OFF -
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