Hitachi Compute Blade 500 Series User Manual page 288

Note: In Write Policy, Write Back with BBU is supported only. If not, write
performance may be degraded.
1 Click Virtual Drives in the main menu.
.
2 From the list displayed at the upper right of the window, select a disk
.
array for which you want to change the write policy. Click Properties >
Go.
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MegaRAID WebBIOS for storage expansion blades
Hitachi Compute Blade 500 Series EFI User's Guide