它控制系统对于任何读操作所能预先读取的页数。

It controls how many pages the system reads ahead for any read operation.

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这个缓存层通过将数据保留一段时间(或者随即预先读取数据以便在需要是就可用)优化了对物理设备的访问。

This caching layer optimizes access to the physical devices by keeping data around for a short time (or speculatively read ahead so that the data is available when needed).

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