How does the kernel determine minimum_io_size and optimal_io_size?

Solution Verified - Updated -

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 storage vendor 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 HDS storage box change its reported I/O size to 65536/44040192 when storage vendor host mode 68 is turned on?

Environment

  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux 7

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