In practice, buffering may occur at various other levels, such as on the hard disk itself, the controller, or the kernel disk drive device driver, so ours may not make much of a difference.
实际上，缓冲可能发生在其它不同的级别，例如硬盘本身、控制器或内核磁盘驱动设备驱动程序，所以我们的工作可能对性能影响不大。
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