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-   -   3.6T useable on a 4TB HDD? (http://www.linuxquestions.org/questions/slackware-14/3-6t-useable-on-a-4tb-hdd-4175489686/)

luckyknight 12-31-2013 06:39 AM

3.6T useable on a 4TB HDD?
 
I've purchased 2 x 4TB WD40EZRX SATA HDDS and setup in parted using a gpt label:

Quote:

GNU Parted 3.1
Using /dev/sdb
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) p
Model: ATA WDC WD40EZRX-00S (scsi)
Disk /dev/sdb: 4001GB
Sector size (logical/physical): 512B/4096B
Partition Table: gpt
Disk Flags:


Number Start End Size File system Name Flags
1 1049kB 4001GB 4001GB ext4 primary
But df -h only shows 3.6T is useable - is this normal?

Quote:

/dev/sdb1 3.6T 855G 2.6T 25% /storage/sdb1
/dev/sdc1 3.6T 2.1T 1.4T 62% /storage/sdc1
Motherboard is a Gigabyte D525 Atom running Slackware 14.1. Disk was formatted using mkfs.ext4

druuna 12-31-2013 07:00 AM

There could be 2 things that could explain this:

1 - When you format a partition a certain percentage (default is 5%, which is 200 Gb in your case) is allocated for root use only, this to make sure you are able to troubleshoot the partition if something goes wrong.

2 - There is a difference between 4 TB as mentioned by the manufacturer and 4 TB as mentioned by df. The first is based on 1000 being 1 Mb and the second on 1024 being 1 Mb.

Those 2 combined will account for the "missing" space.

cascade9 12-31-2013 07:57 AM

Yep, its going to be the whole MB vs MiB issue.

http://en.wikipedia.org/wiki/Mebibyte

4TB = 3.63 TiB.

anscal 12-31-2013 11:46 AM

Quote:

Originally Posted by luckyknight (Post 5089571)
But df -h only shows 3.6T is useable - is this normal?

It is normal, because
Quote:

df -h
reports sizes in MiB/GiB/TiB (i.e. the units we called MB/GB/TB in our childhood :) ). To obtain the base-ten sizes, try
Quote:

df -H
or, better,
Quote:

df --si
:)

luckyknight 12-31-2013 01:13 PM

Quote:

Originally Posted by cascade9 (Post 5089595)
Yep, its going to be the whole MB vs MiB issue.

http://en.wikipedia.org/wiki/Mebibyte

4TB = 3.63 TiB.

I had the same thought as I left the house!! Thanks for clarifying :)


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