How does the kernel determine minimum_io_size and optimal_io_size ? - Red Hat Customer Portal

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Issue

How does the kernel derive the values for minimum_io_size and optimal_io_size?
Can we change the minimum_io_size and optimal_io_size?
How do we change optimal_io_size?
Enabling host mode 68 ("Support Page Reclamation for Linux") in our storage system (HDS VSP G200) causes the I/O size to change from "I/O size (minimum/optimal): 512 bytes / 512 bytes" to "I/O size (minimum/optimal): 65536 bytes / 44040192 bytes". Why does the I/O size become 65536/4404019 when host mode 68 is turned on?

Environment

Red Hat Enterprise Linux 6

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