Block I/O - Jiajun的编程随想

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Block I/O

| b) The entire request queue is kept sorted, sectorwise, so that all seeking | activity along the queue moves (as much as possible) sequentially over the | sectors of the hard disk.This is similar to the algorithm employed in | elevators ------ try to move gracefully in a single direction.

#. Linus Elevator: The Linus Elevator I/O scheduler performs both
   front and
   back merging.
#. The Deadline I/O scheduler: ensure that write requests do not
   starve
   read requests.
#. The Anticipatory I/O scheduler aims to continue to provide
   excellent
   read latency, but also provide excellent global throughput.
#. The Complete Fair Queuing (CFQ) I/O scheduler is an I/O scheduler
   designed for specialized workloads, but that in practice actually
   provides
   good performance across multiple workloads.It is now the default
   I/O scheduler
   in Linux(2.6).
#. the Noop I/O Scheduler truly is a noop, merely maintaining the
   request queue in near-FIFO order, from which the block device
   driver can pluck
   requests.