Windows 7: SSD capacity query

I notice that both the Sandisk Extreme and Crucial M4 had similar drops in the stated capacity when I went to prepare them with the diskpart feature.




The drop was around 9GB - Sandisk 120GB to 111GB and the Crucial M4 128GB to 119GB - yet the Samsung 120GB had little to no drop in reported capacity.


Is this normal?

Not that I've heard of.

Maybe Samsung is using the "other" method of calculating space.

The loss is usually between 6.9% and 7.0%.

Are you using the same tools to format and measure the 3 brands?

Yep I use Wolfgangs tut on the same machine.

Not sure of what you mean the other method though.

There are 2 methods of calculating space. That's why you usually get that 7% loss. The formatted space measurement uses one method. The advertised space uses another.

Maybe Samsung's advertised space is the same as formatted. That is--their so called 120 GB drive would be advertised at maybe 129 if sold by Crucial. 129 x .93 = 120.

Yeah I guess the only way to actually find out would be to take it apart and calculate the capacity form the number of chips contained in and that assuming one would know the capacity of each chip.

But it does leave you wondering why the Sandisk and the Crucial both of 128GB have such differing "final" capacities. I don't know about anyone else but the Sandisk capacity is considerably down on the M4 and is it really worth the bother of getting the Sandisk for less price as it would seem that you end up with less anyway.

I only got it because of the price and the benchmarking against the Samsung which showed up the Sandisk as being very close if not as good as the Samsung.

It would also be not unreasonable for us to expect that they put the final capacity on their ads for these things too don't you think?

You mean by law?

Otherwise, it's not likely. Given a choice between Brand X with 128 gb and Brand Y with 120, the average mouth-breather is going to go for the 128, regardless of "final capacity".

It's all about marketing, and how the capacities are represented. The disks are advertised using the decimal version of Giga, so they are correctly stating the capacity. Let's do the calculations and see how they compare with your figures.

128GB (as advertised) = 128 x 10^9 (decimal Giga)= 128,000,000,000 bytes
128,000,000,000 / 1024^3 (binary Giga) = just over 119GiB

120GB = 120 x 10^9 = 120,000,000,000
120,000,000,000 / 1024^3 = 111.75GiB

Both these sets of figures tie in with what you have above. As regards the Samsung drive, it is possible that this is in fact a 128GB model that has been marked up, not in the decimal sense of GB, but rather in the binary sense. Incidentally, look closely at the capacity marking of this drive. Is it marked as GB or GiB ? GB is the convention used for decimal Giga, whereas GiB is the binary version. Unfortunately, there is no conistency in their use.

Well one lives and learns eh and I think that the average mug like me sees the higher rate as gospel and well someone my age should know better by now that theres no such thing as free lunch eh?

I suppose it's all in the semantics - clever people.

It's all Microsoft's fault. Windows counts a gigabyte as 1,073,741,824 bytes, it's binary form. Drive makers count a gigabyte as 1,000,000,000 bytes, its decimal form.

To make it more confusing, RAM vendors count a GB as they should be, in binary form.