System Option Modes - Hitachi G200 User Manual

3 Control memory can be removed from the storage system by your service
.
representative. Contact Hitachi Data Systems customer support for
adding or removing cache memory.

System option modes

To provide greater flexibility, the Hitachi storage systems have additional
operational parameters called system option modes (SOMs) that allow you to
tailor the storage system to your unique operating requirements. The SOMs
are set to their default values at installation and can be changed only by your
Hitachi Data Systems representative.
The following table lists and describes the system option modes related to
TrueCopy operations. For a complete list of all SOMs, see the Hardware Guide
for your storage system model. Work with your Hitachi Data Systems team to
make sure the appropriate SOMs are set on your storage system.
Note: The SOM information might have changed since this document was
published. Contact your Hitachi Data Systems representative for the latest
SOM information.
Option
mode
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Hitachi TrueCopy® User Guide for Hitachi Virtual Storage Platform Gx00 and Fx00 Models
Allows you to slow the initial copy and resync operations when the write-
pending rate on the RCU exceeds 60%.
• ON: The initial copy and resync copy operations are slowed down when
the write-pending rate on the RCU exceeds 60%.
If the write-pending rate of the CLPR to which the initial copy S-VOL
belongs is not over 60% but that of the MP PCB to which the S-VOL
belongs is over 60%, the initial copy operation is slowed down.
• OFF (default): The initial copy and resync copy operations are not
slowed down when the write-pending rate on the RCU exceeds 60%.
Notes:
1 This mode can be set online.
.
2 The micro-programs on both MCU and RCU must support this mode.
.
3 This mode should be set when requested by the user.
.
4 Setting this mode to ON is recommended when GAD is installed, as the
.
performance degradation is more likely to occur due to active-active
I/Os.
5 If the write-pending status remains at 60% or higher on the RCU for a
.
long time, it takes extra time for the initial copy and resync copy to be
completed due to the slower copy operations.
6 Do not set this mode if the primary or secondary system is connected
.
to USP V/VM with microcode earlier than 60-02-xx-xx/xx. If this mode
is applied and the write-pending rate reaches 60%, pair suspend might
occur.
7 As this mode is enabled per storage system, in an environment where
.
TC and GAD are used, the mode is applied to both program products.
When GAD is installed in a storage system that already uses TC, TC
initial copy might take longer time.
Planning for TrueCopy
Description