Is data accessed from cache counted as I/O?

Yes! Because I/O Express is transparent to the system, any read I/O accessed from cache is believed by the system to be satisfied from disk. The system does not even know that there is a cache. I/O Express, which is a driver, redirects a portion of the read I/Os to the cache and the system counts them as Read I/Os, unaware that the I/O was not satisfied from disk.

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