NEC Express5800 Series Maintenance Manual page 145

Chapter 2 Useful Features
(b) CONFIGURE VIRTUAL DRIVE PARAMETERS setting item
"Virtual Drive Definition" is the item that can be set when creating the Virtual Drive by "Configuration Wizard".
Item
RAID Level
Strip Size
Access Policy
Read Policy
Write Policy
IO Policy
Drive Cache
Disable BGI
Write
Policy
The Disk Cache Policy has the following modes. Select a mode suitable for your environment.
Unchanged
Enable
Disable
Parameter (initial value is in type.)
RAID 0 / RAID 1
64 KB
RW / Read Only / Blocked
No Read Ahead
Write Through
Direct
Unchanged / Enable / Disable
No / Yes
Write Through
 The controller uses the default write cache policy of Physical Device.
 The default value may not be identical to the factory-set value, therefore, do
not specify this mode.
 The controller always uses the write cache policy of Physical Device.
 Be sure to use UPS when you select this mode for disk cache policy.
 The controller does not use the write cache policy of the Physical Device.
 This mode can provide the highest data security, however, the writing
performance is lower than that in Enabled mode.
 It is recommended to use this mode for the sake of data security.
Important

"Unchanged" of the disk cache setting is not supported.

If Enabled is specified for Disk Cache Policy, the controller uses the write
cache policy of the Physical Device. Accordingly, the data in cache
memory of the Physical Device may be lost at an occurrence of power
failure.

Be sure to use UPS when you select Enabled mode for disk cache policy.
Express5800/B120f Maintenance Guide
4. RAID System Configuration
Remarks
Recommended value: RW
WriteThrough: Constant Write Through
Recommended value: Direct
Recommended value: Disable
Specify whether to perform Background
Initialize after creation of VD.
Recommended value: No
Write through mode
The controller does not use cache memory
for writing data. This mode can provide the
highest data security, however, the writing
performance is lower than that in write
back mode.
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