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Upstream kernel allows disabling io merging completely thru this patch:-

488991e2 : block: Added in stricter no merge semantics for block I/O

Not just fcoe, this is required to measure true IOPS for any block device.

1. setup few luns
2. run io using fio with high qd=64 for any size.
  
Actual results:

fio and target both would show significant mergeing.

Expected results:
No merging required to measure true IOPS.

This change went into 2.6.33, and is already in the  RHEL7 kernel.  Closing