Users guide

141 Intel® RAID Software User Guide
8.6 Setting Drive Parameters
The following fields are displayed in the VD Definition screen (see Figure 67 and
Figure 71), which can be used to set the virtual drive parameters:
• RAID Level:
— RAID Level 0: Data striping
— RAID Level 1: Data mirroring
— RAID Level 5: Data striping with parity
— RAID Level 6: Distributed Parity and Disk Striping
— RAID level 10: Striped mirroring
— RAID Level 50: Striped RAID 5
— RAID Level 60: Distributed parity, with two independent parity blocks per
stripe
• Stripe Size: Specify the size of the segment written to each disk. Available stripe
sizes are 4, 8, 16, 32, 64, 128, 256, 512, and 1024 Kbytes.
• Access Policy: Select the type of data access that is allowed for this virtual drive.
The choices are Read/Write, Read Only, or Blocked.
• Read Policy: Enables the read-ahead feature for the virtual drive. Read Adaptive is
the default setting.
— Normal: The controller does not use read-ahead for the
current virtual drive.
— Read-ahead: Additional consecutive stripes
are read and buffered into cache.
This option will improve performance for sequential reads.
— Adaptive: The controller begins using read-ahead
if the two most recent disk
accesses occurred in sequential sectors.
• Write Policy: Determines when the transfer complete signal is sent to the host.
Write-through caching is the default setting.
— Write-back caching (Further classified as W
rite Back with BBU or Always
Write Back, which means Write Back is always enabled even if BBU is bad or
missing): The controller sends a data transfer completion signal to the host
when the controller cache receives all of the data in a transaction. Write-back
caching has a performance advantage over write-through caching, but it
should only be enabled when the optional battery backup module is installed.
The risk of using Always Write Back should be fully recognized.
— Write-through caching: The controller sends
a data transfer completion signal
to the host after the disk subsystem receives all the data in a transaction. Write-
through caching has a data security advantage over write-back caching.
Caution: D
o not use write-back caching for any virtual drive in a Novell NetWare*
volume.
• IO Policy: Applies to reads on a specific virtual drive. It does not affect the read-
ahead cache.