User's Manual

USC and USC - LCE 51
• 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.
LC1_2.book Page 51 Wednesday, November 18, 2009 9:42 AM