11.10. Case study with exercises: Management of a disk block cache
11.10.1. Disk read and write and the requirement for buffers and a cache
We shall assume a conventional file I/O model rather than files mapped into virtual memory. A read or write request from a client of a filing system typically specifies a byte sequence. Let us assume that such a request has been converted by the filing system into a request to read or write a subsequence of bytes from or to some disk block. In practice a requested byte sequence may span more than one disk block, but we can generalize to this from the single block case.
It is necessary to have buffers to hold blocks of information on their way to or from the disk. The client program requires a subsequence ...
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