Equal same sized partitions different used space?

[Deanodarlo]

I've just installed two Toshiba 3TB hard drives - same manufacturing month and firmware.

I created thee GPT partitions on each:

500GB
2TB
240GB

When I format them, some of the identical partitions have different amounts of used space.

eg.

Drive 1 500GB 145MB Used
Drive 2 500GB 105MB Used
Drive 1 240GB 137MB Used
Drive 2 240GB 97.3MB Used

The 2TB partitions however shows exactly the same Used space of 153MB on each drive.

Can anyone think of a reason for this?
Could it be the manufacturer has pre-mapped out bad sectors and therefore there is more used space on one of the drives? Seems strange the difference between both the 500GB and 240GB partitions used space is the same - about 40MB?

If it is pre-mapped bad sectors I'm not bothered, just wondered why the used space is different on freshly formatted identical partitions.

 

[Elixer]

If these are system partitions, they could have hidden system files on them.

 

[Deanodarlo]

An SSD is the system partition. These are fresh 3TB hard drives used for storage only.

I tried to make identical single 2.73TB partitions on the two hard disks and formatted them.

Again I have a difference in formatted used space.

Drive 1 has 173MB used space
Drive 2 has 133MB used space

Seems I have recovered 40MB by going down to a single partition on each drive. Still the difference remains.

Can't work out why they are different? The used space on a fresh format should be the same unless Windows or the motherboard adds some extra files to one of the drives in case of booting?

 

[dave_the_nerd]

Recycle and shadow copy data?