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19 Creating RAID Using Lifecycle Controller
2.11 Size
Type the size of a virtual disk. Minimum value must be 0.1GB and maximum value depends on the total
number of HDDs selected, HDDs’ sizes, and the RAID level.
2.12 Stripe Element Size
The stripe element size is the disk space a stripe uses on each HDD. Select the required stripe element size
from the drop-down menu. Use the up- and down arrow keys to display all options.
2.13 Read Policy
This attribute provides you the following three options for the read policy:
 Read Ahead — The controller reads sequential sectors of the virtual disk when requesting for data.
The Read Ahead policy may improve server 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 server 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 recently
read requests access sequential sectors of the HDD. If the recently read requests access random
sectors of a HDD, the controller uses the No Read Ahead policy.
2.14 Write Policy
This attribute provides you the following three options for the write policy:
 Write Through — The controller sends a write-request completion notification only after the data is
written to the HDD. The Write-Through policy provides better data security than the Write-Back
policy, because the server assumes the data is available only after it has been written to the HDD.
 Write Back — The controller sends a write-request completion notification after the data is in the
controller cache, but has not yet been written to HDD. The Write-Back policy may provide faster
‘write’ performance, but this method also provides less data security because when server stops
functioning, the data which is in the cache memory is lost and therefore data will not be written to
the HDD.
 Force Write Back — The write cache is enabled regardless of whether or not the controller has an
operational battery. If the controller does not have an operational battery, data loss may occur in
the event of nonavailability of power.
2.15 Enable T10 Protection Information Capability
T10 Protection Information Capability also known as DIF (Data Integrity Fields) and the supporting HDDs
are referred to as DIF drives. The T10–enabled HDDs are validated and store data integrity fields for each