SSD capacity affects performance?

[whome88]

So I was just looking through differences in different Plextor M3 SSD models, and something caught my eye. The larger capacity drives had better performance in sequential reads and writes, while lower performance in Random reads and writes.

For example the Px-256M3: Sequential Read (MB/S) 510 Sequential Write (MB/S) 360
Random Read (IOPS 4K) 70,000 Random Write (IOPS 4K) 65,000

Now the PX-512M3: Sequential Read (MB/S) 525 Sequential Write (MB/S) 445
Random Read (IOPS 4K) 56,000 Random Write (IOPS 4K) 30,000

What is it that causes the drive to have the different read/write speeds when the overall capacity is the only difference? Aren't the components within the drive the same, just some drives have more NAND?

Is there a "sweet spot" in terms of size (capacity) and performance? And does this mean that a terabyte SSD (when/if those come out) would also have better performance in sequential read/write and lower specs in random read/write?

 

[claysm]

Larger SSD's usually contain more information channels and as a result the larger drives can execute more read/write operations per second.

No, a 1TB drive could actually be slower than say a 256GB one because manufacturing restraints in the memory density and the specific NAND used means a limit on available channels.

The sweet spot tends to be the 240-256GB size.