NEC Express5800 120Rj-2 User Manual page 122

User Guide
The Write Policy features the following modes to be used in combination with the
WrtThru for BAD BBU. Select a mode suitable for your environment.
Write Policy WBack
WThru
You can change the parameters for the VD definition except for the RAID level and
Stripe Size. On the WebBIOS Top Menu, click [Virtual Disks], specify the parameters
in the "Policies" frame, and click [Change].
Table 26: Write Policy Modes
Checked
Normal write back mode (recommended)
This mode is available only when the
RAID Battery Backup Unit is installed.
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 secu-
rity.
Write through mode
This mode is recommended when the
RAID Battery Backup Unit is not installed.
The controller does not use cache mem-
ory for writing data.
Figure 73: Virtual Disk Definition Screen
WrtThru for BAD BBU
Constant write back mode
This mode is available even if the RAID
Battery Backup Unit is not installed.
The controller always uses cache mem-
ory for writing. In this mode, the data in
cache memory may not be protected
from being damaged 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.
* 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.
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Unchecked