Asus PIKE 2108 - Manual (Page 38)

2-24 Chapter 2: RAID configuration
• 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:
◊ Normal: This disables the read ahead capability.
◊ 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.
◊ Write Back with BBU: 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 has to be used
with a Battery Backup Unit (BBU). This is the default.
• 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.
◊ Cached: In cached I/O mode, all reads are buffered in cache memory.
This is the default.
• Drive Cache: Specify the drive cache policy:
◊ NoChange: Leave the current drive cache policy unchanged. This is
the default.
◊ Enable: Enable the drive cache.
◊ Disable: Disable the drive cache.
• Disable BGI: Specify the background initialization status: