The Fastest 2TB Volume is on a 4TB Drive

See Why You Need More Space Than You Need for the reasons why hard drives slow down as they fill up.

Drives aren’t useful when empty; we fill them up with stuff, like a huge closet!

For maximum performance, get 4TB drives (7200 rpm) for higher speed, even if far less capacity is needed.

The fastest 2TB of hard drive storage is on the largest capacity drive

Update, early 2015: see also 4/5/6TB Hard Drives: Higher Capacity Boosts Real-World Performance.

Assuming the same rotational rate and similar technology, the fastest 2TB of storage is on the largest capacity drive, by simple math (rpm, circumference and data density).

Supposing your storage needs are less than 2TB (or 1TB or 3TB, whatever). Suppose also that you value high performance, especially for new data (e.g., images) that you are adding regularly.

As a drive fills up, all your new stuff, the stuff you’re working on (such as new pictures), is stored onto the slowest part of the drive, because the faster parts of the drive have already been filled up.

This is true not just for sequential I/O speed (reading/writing large files), but also for seek time, because the higher capacity drive stores the same amount of data in fewer tracks, which requires shorter physical movements of the drive heads.

Test results

The graph below compares three Hitachi 7200 rpm hard drives, using a 2TB partition on each drive:

• Hitachi Deskstar 4TB 7K4000
• Hitachi Deskstar 3TB 7K3000
• Hitachi Deskstar 2TB 7K2000

Observe the big picture: the 2TB partition on a 4TB drive is fastest by far. The 4TB drive also offers more consistent speed than the 3TB or 2TB drives.

The 2TB partition on the 3TB drive is slower than on the 4TB drive, but faster than the 2TB drive.

Click for a larger graph.

Accessing 2TB of data on a 4TB, 3TB, 2TB hard drive