Two new 500GB drives but they are different?

I just received two 500GB Blue drives from Amazon. But by looking at it and holding them it’s obvious they are different. One is lighter and they look completely different.

From the web apparently one drive has two 320GB platters and the other drive has one 500GB platter.

So now they have two different characteristics. The one platter drive has faster read rates, but slower random access. I’d rather have faster random access and slightly lower transfer rates. Now I need to order a third drive and hopefully I don’t get one with two 250GB platters. I need them to be the same so both identical PCs have identical performance, otherwise if one is faster I will never hear the end of it.


Could you please provide the exact model numbers of the two drives, and links for the posting or description.  I’m curious to lean more about the characteristics you are describing. ???


WD5000AAKS-00V1A0 and the WD5000AAKS-22A7B2

I’m not sure right now which is the single platter and which is the dual platter since I’m not at home to look at them.(I copied the info from my registration page) But they do have different casings and one is noticeably lighter when you hold them in your hands.

Here is a link that shows and talks about the two platter version.

Here is a link talking about the single platter version

My drives look like what is pictured in each link and the performance I measured was similar to what they got in those links too.

I wonder if there was a short period of time where it was more cost effective to manufacture a lower capacity drive with a higher density platter.