Stated Drive Capacity Less Than Expected

Hi.

This question is not quite the normal question that it appears.

My SSD is stated as being a 128 GB drive, but only displays 117 GB. I am fully aware of the difference between the decimal and binary equivalent values. That is, the stated value of the drive is 128 GB decimal (126,494,961,664 Bytes - near enough to 128 billion bytes (thousand million, for us Brits) ) . The value displayed in the drive's properties is 117 GB binary. These values equate.

However, my problem is that I would have expected the drive to be 128 GB binary (137,438,953,472 Bytes) as, unlike say a HDD, the SSD is manufactured in a 'binary' way (so I am led to believe), in this case 2^37. (This would mean that the drive should have been stated as being a 137 GB drive.) It would seem unlikely that a '128 GB' drive would have a 64 GB bank plus a 32 GB bank plus a 16 GB bank plus a 4 GB bank plus a 1 GB bank just to get a 128 GB drive.

If this is true (that the drive is manufactured in a 'binary' way) then there is a discrepancy of nearly 11 GB. Is this a system block, and if so, how is it used?

Is someone able to explain the discrepancy for me, please.

Matt

See this link:
Why Do Hard Drives Show the Wrong Capacity in Windows?

Thanks zbook for pointing me to this, I appreciate the help. However, it still doesn't help. As stated in my previous post, I am aware of the difference in decimal and binary; the free space is not relevant; not sure about the shadow storage as this give values of 3.5, 4 and 23 GB, none of which is 11; and the partition information still only totals around 119GB. All this still doesn't explain the 'lost' 9-11GBs. But I do appreciate the comment.

Matt

Basically it is the controller chip and the SSD management functions which are very different on an SSD. Memory cells are shuffled around to even out wear or replaced, and whatever the manufacturer decides is the best way to do that and other tasks.
Some may have extra memory/cache used for that purpose, some don't, depends, varies with manufacturers.

The over provisioning on an SSD is around 8-10% of capacity or something like that, much more than the extra spare sectors on an HDD. I know that is not what you are asking about.

128 GB is more a model number convention than an accurate statement of the actual usable capacity, for details you will have to contact the drive manufacturer.

The manufacturers do not want to change the "normal expectation" of actually getting less capacity than stated.
For one of the popular Samsung SSD drives:
"* Actual usable capacity may be less (due to formatting, partitioning, operating system, applications or otherwise)"

Because of the way they are addressed and used RAM module capacity must be a power of 2. SSD manufacturers are not under these constraints and can have whatever capacity is convenient, not necessarily a power of 2. A portion of this is reserved for over provisioning and not included in advertised capacity. What remains is expressed as a rounded decimal number, just as with conventional drives.

There is no discrepancy.

Thanks all for your replies. Some of them, however, to me, invite more questions than they answer.

Not sure what a 'disk management wide-display' is. All visible partitions add up to around 119 GB.

I've heard of this 'shuffling' in order to reduce wear on more used areas. Not sure how the 'over provisioning' works. Is this part of the 'shuffling'? The 8-10% does seem to agree with the results I got.

Isn't a RAM module and an SSD the same sort of thing - i.e. solid state - which would require a power of 2 format, unlike a HDD which, to all intent and purpose, is a 'length' of magnetic 'tape'?

Does the controller chip swap around this reserve, therefore always keeping aside a different portion, which is then not included in the size?

If any of these questions sound ridiculous, it just shows my ignorance, which I fully admit to.

Matt