Hitachi HUS VM - Page 117

Mode Category Description Default
MCU/R
CU
= OFF (default):The order of data transfer slots from VSP
to an external storage is not guaranteed.In V03 and later
versions, the mode is set to ON before shipment. If the
micro-program is exchanged to a supported version (V03
or later), the setting is OFF as default and needs to be set
to ON manually.Note:1. This mode is applied when
performance improvement at sequential write in UVM
configuration is required.
896 Dynamic
Provisioning,
Dynamic
Tiering
The mode enables or disables the background format
function performed on an unformatted area of a DP/DT
pool.
For information about the operating conditions, refer to
the Hitachi Unified Storage VM Block Module Provisioning
Guide.
Mode 896 = ON:
The background format function is disabled.
Mode 896 = OFF (default):
The background format function is enabled.
Note:
1. The mode is applied when a customer requires the
background format for a DP/DT pool in the
environment where new page allocation (for example,
when system files are created from a host for newly
created multiple DP VOLs), frequently occurs and the
write performance degrades because of an increase in
write pending rate.
2. When the mode is set to ON, 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 setting the mode to ON.
3. When a Dynamic Provisioning VOL that is used as an
external VOL is used as a pool VOL, if the external
pool becomes full due to the background format, the
external VOL may be blocked.
If the external pool capacity is smaller than the
external VOL (Dynamic Provisioning VOL), do not set
the mode to ON.
OFF .
897 Dynamic
Tiering
By the combination of SOM897 and 898 setting, the
expansion width of Tier Range upper I/O value (IOPH) can
be changed as follows.
Mode 897 = ON:
SOM898 is OFF: 110%+0IO
SOM898 is ON: 110%+2IO
Mode 897 = OFF (Default)
SOM898 is OFF: 110%+5IO (Default)
SOM898 is ON: 110%+1IO
OFF .
System option modes
B-21
Hitachi Unified Storage VM Block Module Hardware User Guide