Performance Tuning :: Select Partition Table With Non-partition Key Condition?

I have a table that partitioned into six partitions. each partitions placed in different table space and every two table space placed it on a different hardisk

when I will do query select with the non-partition keys condition, how the search process ? whether the sequence (scan sequentially from partition 1 to partition 6) or partition in a hardisk is accessed at the same time with other partition in other hardisk. ( in the image, partition 1,4 accessed at the same time with partition 2,5 and 3,6)