User guide

B–14 System option modes
Hitachi Unified Storage VM Block Module Hardware User Guide
704 Open To reduce the chance of MIH, this option can reduce the
priority of SI, VM, CoW Snapshot, Flash Copy or Resync
copy internal IO requests so that host IO has a higher
priority. This mode creates new work queues where
these jobs can be assigned with a lower priority.
Mode 704 = ON: Copy processing requested is registered
into a newly created queue so that the processing is
scheduled with lower priority than host I/O.
Mode 704 = OFF: Copy processing requested is not
registered into a newly created queue. Only the existing
queue is used.
Note: If the PDEV is highly loaded, the priority of Read/
Write processing made by SI, VM, Snapshot, Compatible
FlashCopy® V2 or Resync may become lower. As a
consequence the copy speed may be slower.
OFF .
720 Universal
Volume
Manager
(Open)
Supports the Active Path Load Balancing (APLB) mode.
Mode 720 = ON: The alternate path of EVA (A/A) is used
in the APLB mode.
Mode 720 = OFF (default): The alternate path of EVA (A/
A) is used in the Single mode.
Note: Though online setting is available, the setting will
not be enabled until Check Paths is performed for the
mapped external device.
OFF .
721 Open When a parity group is uninsulated or installed, the
following operation is performed according to the setting
of mode 721.
Mode 721 = ON: When a parity group is uninstalled or
installed, the LED of the drive for uninstallation is not
illuminated, and the instruction message for removing
the drive does not appear. Also, the windows other than
that of parity group, such as DKA or DKU, are unavailable
to select.
Mode 721 = OFF (default): When a parity group is
uninstalled or installed, the operation is as before: the
LED of the drive is illuminated, and the drive must be
unmounted and remounted.
Note:
When the RAID level or emulation type is changed
for the existing parity group, this option should be
applied only if the drive mounted position remains
the same at the time of the parity group
uninstallation or installation.
After the operation using this option is completed,
the mode must be set back to OFF; otherwise, the
LED of the drive to be removed will not be illuminated
at subsequent parity group uninstalling operations.
OFF .
Mode Category Description Default
MCU/
RCU