This must be some caching effect.
ah sorry. it was a typo.. the SSD to OMV was 29 Sec. and HDD to OMV was 1.14 Mins.
.. and yes, the disk on my Mac is almost 75% full 2.5 inch 5400 rpm machine. almost 7 years old and hdd status is 'pre-fail'.
once again, thanks for all your help. I came to know a lot