Can't Get Full Drive Capacity in Fdisk

Question

So I recently purchased a 4 TB WD Red for my Linux Server and am now trying to partition it for use. I've already come up against the 2TB limit challenge and decided for ease, I'd just have two partitions that come in under the limit. However, I'm having difficulty getting two partitions which add up to anywhere near the size of the disk.

I created my first partition of +2000GB and it has created the following partition...

Disk /dev/sdb: 4000.8 GB, 4000787030016 bytes
255 heads, 63 sectors/track, 486401 cylinders, total 7814037168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk identifier: 0x00000000

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048  3906252047  1953125000   83  Linux

However when I try to create the second partition using any remaining blocks (I used the defaults in fsdisk for the second partition), it only manages to create a partition in the region of 185GB...

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048  3906252047  1953125000   83  Linux
/dev/sdb2      3906252048  4294967294   194357623+  83  Linux

This is basically just my lsblk...

sdb       8:16   0   3.7T  0 disk  
├─sdb1    8:17   0   1.8T  0 part  
└─sdb2    8:18   0 185.4G  0 part  

I'm sure I must be doing something wrong but even googling around the internet, I'm struggling to work out what it is. It looks as though I'm still being limited to the 2TB thing but I'm not sure if that's my problem or not. Would be grateful some pointers please.

Thanks.

Answer 1

Don't use MBR on a disk with over 2^32 sectors (2TiB, assuming 512-byte logical sectors)!

MBR uses 32-bit sector pointers, so anything with more than 2^32 sectors is simply incompatible with MBR -- or at least, MBR tops out at 2^32 sectors, so you won't be able to use the full capacity of the disk, as you've discovered. There are hackish workarounds that can be used to get up to about twice that capacity, but they're unreliable, especially if the disk is to be used across multiple OSes. (As a side note, you seem to be confusing TB and TiB; they aren't the same. See this page for details.)

Instead, use the GUID Partition Table to partition the disk. You can do this with GPT fdisk (gdisk, sgdisk, or cgdisk), or with most libparted-based tools (parted, GParted, and others). Recent versions of fdisk also support GPT, but Ubuntu 14.04 doesn't yet provide that version. (I think one of the later non-LTS releases does, but I don't recall when it was introduced, in Ubuntu version terms.) GPT fdisk is a GPT-specific tool modeled after fdisk, and so uses GPT by default. The others require explicit commands to use GPT rather than MBR.

If you plan to boot from the disk, you should either switch from BIOS-mode to EFI-mode booting (if your computer supports it) or add a BIOS Boot Partition to the disk. The former approach will also require an EFI System Partition (ESP). Switching to EFI-mode booting is preferable, if your computer supports that option. If you're not booting from the disk, you don't need to worry about this; just partition and use it as you see fit.