LinuxQuestions.org - Is there a standard for flash memory's real capacity?

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Is there a standard for flash memory's real capacity?

For example... 16GB USB flash drive's real capacity is almost 14.8~15.4 GiB.

these are different by each manufaturers or models.

In this situation.... How can I expect real minimum capacity?(GiB or Sectors)

Is there a standard? or de facto?

(I know 'LBA1-03' standard of IDEMA. But that is for only SSD/HDD, not USB flash drive/sdhc)

Short answer is "No".

But actual the true standard is the calculation of what 16 GB works out to in real bytes. However since they do not adhere to what they claim, then it is a Sales and Marketing issue.

Depends how you define a GB
Is a Kb 1000 bytes or 1024 bytes?. It is then multiplied up.
Is it raw capacity or formatted capacity??

Marketing will ALWAYS use the terms that give the largest numbers and often round them up as well.
Life tells you NEVER to believe what a marketing man tells you. Always check for yourself from an alternate source.

Take a look at the back of the box. There's a little table there that lists something like this:

Quote:

1 KB = 1000 bytes
1 MB = 1000 KB
1 GB = 1000 MB
1 TB = 1000 GB

That's nice and all, but that isn't how your computer sees it. Your computer works with something like this:

Quote:

1 KB = 1024 bytes
1 MB = 1024 KB
1 GB = 1024 MB
1 TB = 1024 GB

So if we do a little math...

Code:

$ bc -q

scale=4

a=16*1000*1000*1000

a

16000000000



c=16*1024*1024*1024

c

[b]17179869184[b]



b=a/1024/1024/1024

b

14.9011

The drive has 16,000,000,000 bytes available. But for the drive to show up on the computer as actually 16 GB, there would need to be 17,179,869,184 bytes.
When you divide the number of bytes back out as the computer sees it, then you get your 14.9 GB of actual space.

On top of that, as Dave mentioned, your partition table and filesystem need to use some of that space, so you end up with even less than that. (Though the overhead is pretty small compared to what you "lost" in the marketing explained above)

The correct measure is "a power of two." A kilobyte is 1,024 (2 to the 10th power) bytes. A megabyte is 1,024 kilobytes. And so on.

Quote:

Originally Posted by sundialsvcs (Post 5608699)

The correct measure is "a power of two." A kilobyte is 1,024 (2 to the 10th power) bytes. A megabyte is 1,024 kilobytes. And so on.

Since "mega" is the SI prefix for 10^6, there is some effort to define 2^20 as a Mebibyte.

Won't happen!! At least in general conversation.

Drives are actually what they are claimed to be (generally in small print) but unless you use the drive "RAW" then you won't get that amount and it has been that way for a very long time.

If you want the extra space then use it raw. Might still be in the code.

Quote:

Originally Posted by jefro (Post 5608936)

If you want the extra space then use it raw.

Old tongue-in-cheek question about some floppy diskettes:

"These disks say they are 2 MB unformatted, 1.44 MB formatted. Anyone know of a good unformat utility?"

That is both old and funny. I never heard it. :)