Intel SRCU31 5.2.8.1Downstream Write-Through, 5.2.8.2Sequential Write-Back, RAID Features

				RAID Features
Table 5-13. Disk Actions, Usage and Status
	Disk Action	Usage	Status	Description if Submitted and Confirmed
	None	Available	Formatted OK
	None	Available	Formatting	No action can be taken while the drive is being formatted.
	None	Available	Offline
	None	Available	OK
	None	In Use	Failed
	None	In Use	OK
				No action will be taken.
	None	Pass-	Ok
		through
	None	Spare	OK
	None	In Use	Offline
	Pass-through to			Drive is not controlled by RAID firmware and thus cannot
		Available	OK	be a part of a RAID volume. The drive will be available to
	Host
				the operating system as an individual disk.
	Release Spare	Spare	OK	Convert a spare to an available drive.
		Available, In		Indicates that the disk drive has reported a S.M.A.R.T
	None	Use, Pass-	Alarm-service	event and may be in need of service or replacement. See
		through,		the specific disk drive manufacturer documentation for
		Spare		details including error codes, utilities, etc.
			Incompatible	Drive is not controlled by RAID firmware and thus cannot
	None	In Use		be a part of a RAID volume. The drive will be available to
			Version
				the operating system as an individual disk.

5.2.8Caching

5.2.8.1Downstream Write-Through

The RAID controller cache is used to buffer write data until it is written to disk. Data in the cache is not available to be read from the cache directly. This type of caching is enabled by default when no other cache type (Sequential or Full Write Back) is selected.

5.2.8.2Sequential Write-Back

The host operating system is given a successful write reply immediately while the write data is held in the RAID controller cache until the actual write to disk occurs. Only data determined to be sequential is cached.

5.2.8.3Full Write-Back

The host operating system is given a successful write reply immediately while the write data is held in the RAID controller cache until the actual write to disk occurs. Caching occurs for both sequential and random data.

Note: Intel Integrated RAID software provides write-back cache capability to improve host performance for certain types of applications. Applications which may benefit from the write-back cache

Intel® Server RAID Controller U3-1 User’s Manual Rev 1.0 5-13