Asus PIKE 2208 - Manual (Page 36)

2-22 Chapter 2: RAID configuration
13. If there are additional drive groups with three or more drives each, you can
add them to the virtual drive.
14. Change the virtual drive options from the defaults listed on the screen as
needed.
Here are brief explanations of the virtual drive options:
• RAID Level: The drop-down menu lists the possible RAID levels for the
virtual drive. Select RAID 50.
• Strip Size: The strip size specifies the size of the segment written to
each disk in a RAID configuration. You can set the strip size up to 1 MB.
A larger strip size produces higher read performance. If your computer
regularly performs random read requests, choose a smaller strip size.
The default is 256 KB.
• Access Policy: Select the type of data access that is allowed for this
virtual drive:
◊ RW: Allow read/write access. This is the default.
◊ Read Only: Allow read-only access.
◊ Blocked: Do not allow access.
• Read Policy: Specify the read policy for this virtual drive:
◊ No Read Ahead: This disables the read ahead capability.
◊ Always Read Ahead: This enables read ahead capability, which
allows the controller to read sequentially ahead of requested data and
to store the additional data in cache memory, anticipating that the data
will be needed soon. This speeds up reads for sequential data, but
there is little improvement when accessing random data. This is the
default.
• Write Policy: Specify the write policy for this virtual drive:
◊ Write Through: In Write Through mode, the controller sends a data
transfer completion signal to the host when the drive subsystem has
received all of the data in a transaction.
◊ Always Write Back: In Writeback mode, the controller sends a data
transfer completion signal to the host when the controller cache has
received all of the data in a transaction. This setting is recommended
in Standard mode.
• IO Policy: The IO Policy applies to reads on a specific virtual drive. It
does not affect the read ahead cache.
◊ Direct: In direct I/O mode, reads are not buffered in cache memory.
Data is transferred to the cache and the host concurrently. If the same
data block is read again, it comes from cache memory. This is the
default.
◊ Cached: In cached I/O mode, all reads are buffered in cache memory.