Aggregates are the raw space in your storage system. You take a bunch of individual disks and bind them together into aggregates. But, an aggregate can't actually hold data, until you carve out partitions, which in NetApp land are called volumes. The volumes hold the data.
The block level data will be stripped across the disks that form the aggregates depending on the RAID type.
There is no way that you can say these blocks of data will be written on this specific DISK. The blocks are striped as per RAID technology.