Dell USC, User Manual

Page: 78 / 132

78
USC and USC-LCE Operations
–
Write Through
— The controller sends a write-request completion
signal only after the data is written to the disk. The Write Through
policy provides better data security than the Write Back policy since
the system assumes the data is available only after it has been written
to the disk.
– Write Back — The controller sends a write-request completion signal
as soon as the data is in the controller cache but has not yet been
written to disk. The Write Back policy may provide faster write
performance, but it also provides less data security since a system
failure could prevent the data from being written to disk.
–
Force Write Back
— The write cache is enabled regardless of whether
the controller has an operational battery. If the controller does not
have an operational battery, data loss may occur in the event of a
power failure.
• To assign a hot spare to the virtual disk, select the
Assign a Hot Spare Disk
check box. A hot spare is an unused backup physical disk that can be used
to rebuild data from a redundant virtual disk.
• Select the physical disk to be used as the hot spare from the Hot Spare
Disk drop-down menu.A hot spare can be used only with a redundant
RAID level. Hot spares also have requirements for physical disk size. The
hot spare cannot be smaller than the smallest physical disk included in the
virtual disk. If the RAID level and physical disk availability do not meet
these requirements, the Assign a Hot Spare Disk check box is disabled.
Click
Next
after making your selection.
Advanced Wizard Only - Review Summary
The Summary screen displays the virtual disk attributes based on your selections.
CAUTION:
Clicking the Finish button deletes all existing virtual disks except for
any foreign configurations that you specified should be kept. All data residing on
the deleted virtual disks will be lost.
Click Finish to create a virtual disk with the displayed attributes.
OR
To return to a previous screen to review or change selections, click
Back . To
exit the Wizard without making changes, click Cancel .