Bull NovaScale R460 E2, Руководство пользователя, Страница: 137 / 490

Configuring Your Server 4-53
„
To use RAID 5, RAID 6, or RAID 50, you need to additionally install the optional RAID
Upgrade Kit.
„
If RAID Upgrade Kit is not installed, do not select "RAID5" that may appear in [RAID Level]
box. If selected, you will fail to save the configuration information. In such a case, you need to
define a VD again from the beginning.
The Write Policy has the following modes depending on combination with WrtThru for BAD BBU. Select a mode suitable for
your environment.
WrtThru forBAD BBU
Checked Unchecked
Write
Policy 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
regardless of battery charged status or existence of
battery.
Be sure to use UPS when specifying this mode for write
policy.
WThru 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. * 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.
IMPORTANT:
„
If constant write back mode is selected, the controller operates in write back mode even if the
battery has failed or insufficiently charged. The data in cache memory may be lost at an
occurrence of power failure.
„
Be sure to use UPS when specifying the constant write back mode for write policy.
The Disk Cache Policy has the following modes. Select a mode suitable for your environment.
Unchanged
•
The controller uses the default write cache policy of hard disk drive.
•
The default value may not be identical to the factory-set value, therefore, do
not specify this mode.
Enabled
•
The controller always uses the write cache policy of hard disk drive.
•
Be sure to use UPS when specifying this mode for disk cache policy.
Disabled
•
The controller does not use the write cache policy of the hard disk drive.
•
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:
„
If "Unchanged" is specified for Disk Cache Policy, the default value may not be identical to the
factory-set value, therefore, do not specify this mode.
„
If Enabled is specified for Disk Cache Policy, the controller uses the write cache policy of the
hard disk drive. Accordingly, the data in cache memory of the hard disk drive may be lost at an
occurrence of power failure.
„
Be sure to use UPS when using the cache memory of the hard disk drive.