Users Guide

60 USC and USC - LCE
Advanced Wizard Only - Additional Settings
Use the Additional Settings screen to specify cache policies and stripe
element size. You can also assign a hot spare to the virtual disk.
• Select the stripe element size from the Stripe Element Size drop-down
menu. The stripe element size is the amount of disk space a stripe
consumes on each physical disk in the stripe. The
Stripe Element Size
drop-down menu may contain more options than initially displayed on the
screen. Use the up-arrow and down-arrow keys to display all options.
• Select the read policy from the Read Policy drop-down menu.
– Read Ahead — The controller reads sequential sectors of the virtual
disk when seeking data. The Read Ahead policy may improve system
performance if the data is written to sequential sectors of the virtual
disk.
– No Read Ahead — The controller does not use the Read Ahead policy.
The No Read Ahead policy may improve system performance if
the
data is random and not written to sequential sectors.
– Adaptive Read Ahead — The controller initiates the Read Ahead
policy only if the most recent read requests accessed sequential sectors
of the disk. If the recent read requests accessed random sectors of the
disk, then the controller uses the No Read Ahead policy.
• Select the write policy from the Write Policy drop-down menu.
– 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.
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