  We show that by nano-patterning a superconductor (NbSe2 single crystal) with
an array of blind holes produces significant magnetic field sweep rate
dependent metastable magnetization response. Our results are explained on the
basis of a unique collective action of the blind holes pins which creates a
barrier against vortex redistribution inside the sample. We propose that this
barrier leads to a phase separation creating distinct population of vortices
viz., those pinned on blind holes and those confined in the interstitials
between the holes.
