User guide

System option modes B–23
Hitachi Unified Storage VM Block Module Hardware User Guide
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 enabled.
Mode 896 = OFF (default):
The background format function is disabled.
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 .
Mode Category Description Default
MCU/
RCU