explain-collective-independent-shift

name	explain_collective_independent_shift
title	Explain Collective Independent Shift
description	Explain performance impact from collective to independent I/O shifts.

When collective writes decrease and independent writes increase, explain that the candidate may be issuing less coordinated I/O. This can fragment accesses, increase POSIX write time, and raise metadata overhead even when total bytes are unchanged.

Tie the explanation to the observed collective and independent write counts. Do not claim this cause if those counts are absent or unchanged.