SSD disk capacity reported by manufacturer

starbearer · 11-05-2020, 12:03 AM

I was looking at a disk manufacturer specifications using the data sheet for a SSD disk, when I came across this disk which is being marketed as 512 GB disk.

Capacity LBA Cylinders Heads Sectors User Capacity(MB)

512GB 937703088 16383 16 63 457862

This user capacity is 457 GB or 447 maybe seen on Windows, but that's quite a reduced space, more than 10% of the overall disk capacity. I'm additionally perplexed because this is being marketed as an actual 512 GB disk.

Is this over-provisioning by the SSD disk? In which case should it be marketed as 512 GB? Or is it just that the disk is really 512 GB but on WIndows it's likely to be seen as less due to WIndows' binary system calculation?

beachboy2 · 11-05-2020, 01:07 AM

Gibibyte vs. gigabyte

A gibibyte and a gigabyte are sometimes used as synonyms, though technically they do not describe the same amount of capacity. They are close in size, however. A gibibyte is equal to 230 or 1,073,741,824 bytes. A gigabyte is equal to 109 1,000,000,000 bytes. One gibibyte equals 1.074 gigabytes. That's a 7% difference.

https://searchstorage.techtarget.com...n/gibibyte-GiB

https://www.gbmb.org/gb-to-gib

starbearer · 11-05-2020, 02:30 AM

Quote:

Originally Posted by beachboy2

Gibibyte vs. gigabyte

A gibibyte and a gigabyte are sometimes used as synonyms, though technically they do not describe the same amount of capacity. They are close in size, however. A gibibyte is equal to 230 or 1,073,741,824 bytes. A gigabyte is equal to 109 1,000,000,000 bytes. One gibibyte equals 1.074 gigabytes. That's a 7% difference.

https://searchstorage.techtarget.com...n/gibibyte-GiB

https://www.gbmb.org/gb-to-gib

Yes I understand the difference, but using the data sheet, I am unable to figure out yet, if I plug this disk in Linux, which normally use decimal or gigabyte system, exactly how much capacity I'll have, since there is no indication of base or a comment like "1 Gigabyte = 1 billion bytes" in the sheet.

This is what is reported for capacity -

https://imgur.com/5zMZOAm

mrmazda · 11-05-2020, 03:44 AM

Quote:

Originally Posted by starbearer

Code:

Capacity    LBA    Cylinders Heads Sectors  User Capacity(MB) 
 512GB   937703088   16383    16     63        457862

What exactly produced this?

16383 X 16 X 63 (X 512 = 8063.5 MB) is an anachronism that produces a partitioning format that yields the maximum size known as the 8 GB limit. There's no corelation between 512GB and the rest of the numbers on that line, unless the 457862M is the net available space on one of the partitions.

This 512G SSD I recently installed produces this output using Ubuntu 20.04's fdisk:

Code:

fdisk -l /dev/sda
Disk /dev/sda: 476.96 GiB, 512110190592 bytes, 1000215216 sectors
Disk model: T-FORCE 512GB
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier:...

# gdisk -l /dev/sda
...
Partition table scan:
  MBR: protective
  GPT: present

Found valid GPT with protective MBR; using GPT.
Disk /dev/sda: 1000215216 sectors, 476.9 GiB
Model: T-FORCE 512GB
Sector size (logical/physical): 512/512 bytes
Disk identifier (GUID):..

jefro · 11-05-2020, 04:58 PM

This is what I think is correct.

https://www.wilderssecurity.com/thre...atting.391198/

computersavvy · 11-06-2020, 12:04 AM

I find it hard to believe that people seem to not understand the difference between marketing speak which is based on decimal units and calls a device 500 GB and system numbers that are based on binary units which displays the exact same value as 465.66 GiB. Those of us who have been working with systems for some time (some longer than others) and those who have had training in understanding the differences between decimal and binary numbering systems see it clearly.

Yet others cannot even seem to fathom how to use a modern calculator such as the standard one on my linux distro (and I suspect is the same on most distros) that will do a direct conversion from Gigabytes to Gibibytes. 500 GB = 465.66 GiB is a fact of life. The advertised size of 500GB seems larger but in fact is equal to the usable 465.66 Gib that was displayed repeatedly above.

I have several 3TB drives, but the usable on each is "only" 2.7+TiB -- so it "seems" I lose almost 10% of the size.
Does that bother me? NO, it is a fact that advertised sizes are not stated in binary units.

computersavvy · 11-06-2020, 12:20 AM

Quote:

Originally Posted by mrmazda

What exactly produced this?

Code:

Capacity    LBA    Cylinders Heads Sectors  User Capacity(MB) 
 512GB   937703088   16383    16     63        457862

16383 X 16 X 63 (X 512 = 8063.5 MB) is an anachronism that produces a partitioning format that yields the maximum size known as the 8 GB limit. There's no corelation between 512GB and the rest of the numbers on that line, unless the 457862M is the net available space on one of the partitions.

If you read up on newer drives, both SSD & HDD, there is no real correlation between the C-H-S numbers and the actual geometry of the drive. That is simply electronic magic that allows the system to talk to the drive in terminology that is already understood and they understand each other. As you surmised, the 457862MB (or rather MiB) is the actual usable net space on the device after allowing for unit conversion and reserved space for "bad sector" replacement.

mrmazda · 11-06-2020, 12:44 AM

Quote:

Originally Posted by computersavvy

If you read up on newer drives, both SSD & HDD, there is no real correlation between the C-H-S numbers and the actual geometry of the drive.

I've known about it since last century. If you read back far enough you'll see they comprise a component of the concept of alignment, and are still relevant to those keeping 30-40 year old equipment operational. I see them, and a whole lot more, printed in every partitioning log the non-FOSS partitioner I use exclusively for writes generates.