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To improve RAID 1/10 Write performance, OS drivers need to issue the required Write IOs as Fast Path IOs (after the appropriate checks allowing Fast Path to be used) to the appropriate physical drives (translated from the OS logical IO) and wait for all Write IOs to complete. Design: A write IO on RAID volume will be examined if it can be sent in Fast Path based on IO size and starting LBA and ending LBA falling on to a Physical Drive boundary. If the underlying RAID volume is a RAID 1/10, driver issues two fast path write IOs one for each corresponding physical drive after computing the corresponding start LBA for each physical drive. Both write IOs will have the same payload and are posted to HW such that replies land in the same reply queue. If there are no resources available for sending two IOs, driver will send the original IO from SCSI layer to RAID volume through the Firmware. Based on PCI bandwidth and write payload, every second this feature is enabled/disabled. When both IOs are completed by HW, the resources will be released and SCSI IO completion handler will be called. Signed-off-by: Sasikumar Chandrasekaran <sasikumar.pc@broadcom.com> Reviewed-by: Tomas Henzl <thenzl@redhat.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.