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I just used boot and nuke to wipe my hard drive and reinstall my OS systems. When selecting the hard drive I noticed that there were only 931gb free in my hard drive.

Is this normal? It sees like a strange number as I though terabyte drives held 1024gb.

Is some of the hard drive hidden? Are there any programs that can check?

Thanks in advanced for any help with this!

df -h returns the following:

Filesystem           Size  Used Avail Use% Mounted on
udev                 3.9G     0  3.9G   0% /dev
tmpfs                786M   18M  768M   3% /run
/dev/sda5            437G  5.7G  409G   2% /
tmpfs                3.9G   31M  3.9G   1% /dev/shm
tmpfs                5.0M  4.0K  5.0M   1% /run/lock
tmpfs                3.9G     0  3.9G   0% /sys/fs/cgroup
tmpfs                786M   20K  786M   1% /run/user/124
/home/*/.Private     437G  5.7G  409G   2% /home/*
tmpfs                786M  2.0M  784M   1% /run/user/1000

lsblk returns the following:

NAME           MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
sda              8:0    0 931.5G  0 disk  
├─sda1           8:1    0   500M  0 part  
├─sda2           8:2    0 478.8G  0 part  
├─sda3           8:3    0   496M  0 part  
├─sda4           8:4    0     1K  0 part  
├─sda5           8:5    0 443.9G  0 part  /
└─sda6           8:6    0   7.9G  0 part  
└─cryptswap1   253:0    0   7.9G  0 crypt [SWAP]
sr0             11:0    1  1024M  0 rom   

EDIT: I am literally installing the dual boot system as we speak. Windows first, here is a breakdown of what Windows 10 sees: Windows 10 readout

So total size is 931.51GB. That is a very strange number.

marked as duplicate by mikewhatever, Videonauth, Eric Carvalho, Charles Green, Rinzwind Nov 25 '17 at 15:12

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  • 2
    What are the outputs of df -h and lsblk? edit your question to include that information. And by the way a TerraByte is supposedly 1024 GigaByte. – Videonauth Nov 25 '17 at 9:13
  • 2
    @Berrik on the other hand ravery is right, due to the switch from powers of two to use scientific thousand we now have GiB and GB, one of which is using 1000 where as the other uses 1024 and so on, due to that many programs still show power of two you are left with an amount less than the manufacturer of the drive announces on its label. – Videonauth Nov 25 '17 at 9:35
  • 2
    1 TB = 1,000 GB = 1,000,000 MB = 1,000,000,000 KB = 1,000,000,000,000 bytes = 976,562,500 KiB = 953,674.31640625 MiB = 931.322574615478515625 GiB – jdwolf Nov 25 '17 at 9:42
  • 1
    @Berrik read my comment. – jdwolf Nov 25 '17 at 9:46
  • 1
    @Berrik No. An MiB is 1024 KiB. ~931.51 GiB the size of a 1 TB disk. A 1 TiB is 1,099,511,627,776 bytes. – jdwolf Nov 25 '17 at 9:57
4

The discrepancy with the displayed number is do to the fact that hard drive manufactures are aiming for a number closer to

1,000,000,000,000 bytes which is 1 TB.

while windows and Linux present you with a unit of 1024 not 1000 although on Windows this is GB and on Linux this is the more accurate GiB.

1 TiB would have to be 1,099,511,627,776 bytes.

If we go the nearest GiB with only 1,000,000,000 bytes this is the math:

1,000,000,000,000 bytes / 1024 = 976,562,500 KiB
976,562,500 KiB / 1024 ~= 953,674 MiB
953,674 MiB / 1024 ~= 931 GiB

However don't make the assumption that hard drive manufactures make disk platters that exactly add up to 1,000,000,000,000 bytes they do not. Still the same unit conversion discrepancies apply.

  • Woo. An answer I can understand! For bonus points what's half of 931.51GB in bits? – Berrik Nov 25 '17 at 10:16
  • 2
    931.51GB / 2 = 465.755 * 8 = 3726.04Gb <- note lower case b. – jdwolf Nov 25 '17 at 10:20
  • Thanks again everyone. This cleared up the question I had. Once I install Ubuntu 17.10 I'll update the question with the relevant Ubuntu perspective! – Berrik Nov 25 '17 at 10:24
4

it's because Gigabyte (GB) can have different meanings in different contexts. When referring to computer memory, gigabyte is always a “power of two” = 1,073,741,824 bytes, but when measuring hard drive capacity it is often defined as 1,000,000,000 bytes. Generally, operating systems calculate disk and file sizes using binary numbers, so a new 500 GB drive you've just purchased would be reported by the OS as "465.66 GB" (meaning 465.66 GiB, GiB = Gigibyte). so 1 TB hard disk means 1,000,000,000,000 bytes and if you divide it by 1024^3 to convert it to Gigabytes, you see the result is: 931.322574615 GB

  • Just one minor Correction GB has no different meaning nowhere it is either GiB or GB. – Videonauth Nov 25 '17 at 9:46
  • Right I understand that 1TB means 1,000,000,000,000 bytes and that hard drives vary in size i.e. 1TB is usually 1024GB but I don't understand how you got to "931.322574615 GB". 1024^3 is 1,073,741,824... I think I misunderstood a step... – Berrik Nov 25 '17 at 9:50
  • 1
    1,000,000,000,000 bytes = 1 TB 1,000,000,000,000 / 1024 / 1024 / 1024 = 931.322574615478515625 GiB – jdwolf Nov 25 '17 at 9:53
  • 2
    Well drive manufacturers use the scientific notation Gigabyte (GB) while most programs as well show falsely GigaByte (GB) instead of powers of two GibiByte (GiB). @Berrik see here. – Videonauth Nov 25 '17 at 10:01
  • 1
    Alright time ot actually answer this – jdwolf Nov 25 '17 at 10:02

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