Read/write caching

The comments on read caching and write caching by analogy also apply to read/write caching. With read/write caching, however, conflicts between write data and read data may arise within the available cache area: for instance, a heavy I/O system load may result in the transfer of write data to disk being delayed for some time. This causes more and more of the storage space available in the cache to be filled with write data, proportionally reducing the space available for read data and consequently the number of read hits. Good hit rates should therefore always be of special concern.

With the caching technique “resident buffering”, the situation just described can never arise, since the cache size matches the size of the area it serves.