What is the diff between these two HDs?

[ThomP]

Hi,

I've just purchased 4x ST3146855SS from a popular auction site, but they have instead sent me ST3146755SS.

I am just trying to understand what the core differences are in maybe features or performance.

The ST3146855SS is a Cheetah 15k RPM SAS drive and the ST3146755SS is a Cheetah T10 SAS drive with 15k RPM, 10K performance?

I would be graceful if anyone could advise me in the core differences between these two products.

Thanks.
Thomas.