Reduced capacity on Sandisk MicroSD cards

[CJay]

Those differences also apply to hard drives, friend had 2 4TB drives of the same manufacturer but different "variant" and one had 13GB less.

Firmware differences can often have that effect on hard drives, it was a fairly regular occurrence when ordering a certain make and model of Ultra 320 SCSI drive as a replacement part for a RAID array that the drive was rejected by the controller because some revisions, while having exactly the same model number, would be a minuscule amount lower capacity (8MB springs to mind).

We eventually worked out how to identify the drives by serial number and would request 'lower than' or build new/replacement arrays with an amount of slack in them to allow them to be rebuilt with any capacity version.

[Kilrah]

Friend ran into it when wanting to back up one onto the other and the destination ran out of space. Yup it was that full 

And no it wasn't cluster size difference/hidden files, the disk manager did show the matching difference on total drive size.

[CJay]

Yeah, got GiB and GB swapped again.

Shows how stupid the whole thing is.

Exactly, while I'm all for the correct use of units, it should be just one standard, correct or not, and stuck to.

The hard drive thing I am sure was just taking advantage of SI units to make their drives look larger for marketing as I remember one of the leading PC mags being rather outraged the first time they came across it.

Pretty much all disk capacity until then was defined as binary, needless to say, all the other drive manufacturers caught on *real* quick.

I and a lot of other techs/engineers/users have been brought up to think of GB in binary terms so 1024 is the measure I will always use to define a GB, MB and KB, even if it is correctly GiB,MiB and KiB.

I've been around long enough to know where it fits from the context but so many non techs and newbies have no idea and I've had it 'explained' to me by kitchen table PC experts in some really amusing ways.

[RGB255_0_0]

I can't be bothered explaining Base 10 and Base 2 differences any more. So I follow what the OS and Manufacturers call it: "formatted" capacity. And Apple in IOS also use Base 2.

[Delta]

Drive manufacturers are using the correct units. 'everybody' (that is: Microsoft) uses the wrong units.

I was thinking along those lines, but it doesn't add up...

Old cards
31,914,983,424 Bytes is (nearly) 32 GB, or 29.72 GiB

New cards
31,104,958,464 Bytes is (about) 31 GB or 28.97 GiB

So which even way you spin it, the old cards were (nearly) 32 GB, the new ones are 31 GB.  The old cards were 29.72 GiB, the new ones are 28.97 GiB 

[CJay]

Drive manufacturers are using the correct units. 'everybody' (that is: Microsoft) uses the wrong units.

I was thinking along those lines, but it doesn't add up...

Old cards
31,914,983,424 Bytes is (nearly) 32 GB, or 29.72 GiB

New cards
31,104,958,464 Bytes is (about) 31 GB or 28.97 GiB

So which even way you spin it, the old cards were (nearly) 32 GB, the new ones are 31 GB.  The old cards were 29.72 GiB, the new ones are 28.97 GiB 

I was about to check my two Sandisk Extreme cards, one shows 28.79GiB in disk management, the other, in the same adapter, started to smell of burning and got too hot to touch. It's not recognised at all now.

So, I guess I need to get that one replaced and try again later

(Both appear identical under a 4x loupe and were bought from Costco)

[Monkeh]

Drive manufacturers are using the correct units. 'everybody' (that is: Microsoft) uses the wrong units.

I was thinking along those lines, but it doesn't add up...

Old cards
31,914,983,424 Bytes is (nearly) 32 GB, or 29.72 GiB

New cards
31,104,958,464 Bytes is (about) 31 GB or 28.97 GiB

So which even way you spin it, the old cards were (nearly) 32 GB, the new ones are 31 GB.  The old cards were 29.72 GiB, the new ones are 28.97 GiB 

Never said I thought it was a unit issue. They appear to be cutting corners.

[stj]

the firmware in the card pre-allocates some of the flash for re-mapping bad blocks in the future.
different firmware,controller or even trust in the flash lifespan could effect the size of the pre-allocated space.
 

[amyk]

31914983424, which is apparently the size of the "good" card, is not even a "HDD manufacturer's GB" or an "SI GB". If you bought a "32GB" HDD you would now expect at least 32000000000 bytes. Is there a "flash memory GB" which is exactly 997343232 bytes, and they're now trying to cut that down to 972029952?

Note that 997343232 is exactly 16384*60873, and 972029952 is exactly 1048576*927 (927 "real" MB).

I would demand a refund, tell Sandisk about it, and spread this news over the Internet. Selling "32GB" of storage which has <32000000000 bytes is not even correct according to SI.

As for the "explanations" about spare area/extra space, that is just wrong. Flash comes in binary capacities and small integer multiples thereof, with an extra "spare area" in each page specifically for block mapping and error correction codes. A 32GB (256Gb) flash like this one has 16384 blocks * 256 pages * 8640 bytes/page = 36238786560 bytes. That would be 36GB in HDD manufacturer's units, or 33.75 binary GB. Even if you cut that down to 32000000000 actual accessible storage space, there's still 4238786560 bytes (4GB+) of spare area, or nearly 1/8th of the total bits on the device. If they really need more than that amount of spare area, then they should not call them 32GB, but 31GB.

[ez24]

Never said I thought it was a unit issue. They appear to be cutting corners.

Some VP got a bonus for saving the company money (smaller die size).  FYI I just got a new box of saltine crackers from Costco and they are 1/8 inch smaller than the box I got last month.  One of their VP's got a bonus also.  In other words making the product smaller makes VP bonuses.  So someone made out.