Asus PIKE II 3108 Series Manual page 29

Strip Size – The strip size is the portion of the stripe that resides on a single virtual
drive in the drive group. Strip sizes of 64 KB, 128 KB, 256 KB, 512 KB, or 1 MB are
supported.
Read Policy – Specify one of the following options to specify the read policy for
this virtual drive:
Normal – Read ahead capability lets the controller read sequentially ahead
of requested data and to store the additional data in cache memory, thereby
anticipating that the data will be needed soon. This process speeds up
reads for sequential data, but there is little improvement when the computer
accesses random data.
Ahead – Disables the read ahead capability.
Write Policy – Select one of the following options to specify the write policy for this
virtual drive:
Write Thru – In this mode, the controller sends a data transfer completion
signal to the host when the drive subsystem has received all the data in a
transaction. This option eliminates the risk of losing cached data in case of a
power failure.
Write Back – In this mode, the controller sends a data transfer completion
signal to the host when the controller cache has received all the data in a
transaction.
Write Back with BBU – In this mode the controller has no BBU or the BBU
is bad. If you do not choose this option, the controller firmware automatically
switches to the Write Thru mode if it detects a bad or missing BBU.
The write policy depends on the status of the BBU. If the BBU is not present, is
low, is failed, or is being charged, the virtual drive is still in the Write Back mode
and there is a chance of data loss.
I/O Policy – The I/O policy applies to reads on a specific virtual drive. It does not
affect the read ahead cache.
Cached – In this mode, all reads are buffered in cache memory. Cached I/O
provides faster processing.
Direct – In this 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. Direct I/O makes sure that the
cache and the host contain the same data.
ASUS PIKE II 3108 Series 2-15