NEC Express5800/A1080a, User Manual, Page: 374 / 696

Hardware
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The Write Policy has the following modes depending on combination with WrtThru for BAD BBU.
Select a mode suitable for your environment.
WrtThru for BAD BBU
Checked Unchecked
WBack Normal write back mode
(recommended)
The controller uses cache
memory for writing.
However, if the battery is
being charged or failed, the
controller operates in WThru
(write through) mode
automatically. Thus, this
mode can provide higher data
security. Constant write back mode
The controller always uses
cache memory for writing. In
this mode, the data in cache
memory may not be protected
from being lost if the power
failure occurs due to
charge/discharge or defect of
the battery. Be sure to use UPS
when specifying this mode for
write policy. Write Policy
WThru Write through mode
The controller does not use
cache memory for writing
data.
This mode can provide
higher data security,
however, writing performance
is lower than that in WBack
mode. * This mode is unavailable.
If you do not check "WrtThru for
BAD BBU" at creation of VD,
this item is automatically
checked after the VD has been
created.
You can change parameters for VD definition except for RAID Level and Stripe Size. On the
WebBIOS Home Menu, select [Virtual Disks], press
Enter , and specify parameters in "Policies"
frame, then select [Change] and press Enter .