Aren't 2TB+ disk sizes supposed to be standardized?

Aren't 2TB+ disk sizes supposed to be standardized?

[Tudor Holton]

Hi guys,

I just discovered this when I was about to do a disk transfer:

[edited for brevity]

$ sudo fdisk -l
Disk /dev/sdc: 2000.4 GB, 2000397852160 bytes
255 heads, 63 sectors/track, 243201 cylinders, total 3907027055 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: 0x00027892
Disk /dev/sdd: 2000.4 GB, 2000398934016 bytes
255 heads, 63 sectors/track, 243201 cylinders, total 3907029168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

$ sudo smartctl -a /dev/sdc
Model Family:     Seagate Barracuda (SATA 3Gb/s, 4K Sectors)
Device Model:     ST2000DM001-1CH164
Firmware Version: CC43
User Capacity:    2,000,397,852,160 bytes [2.00 TB]
Sector Sizes:     512 bytes logical, 4096 bytes physical
ATA Version is:   8
ATA Standard is:  ATA-8-ACS revision 4

$ sudo smartctl -a /dev/sdd
Model Family:     Seagate Barracuda LP
Device Model:     ST32000542AS
Firmware Version: CC34
User Capacity:    2,000,398,934,016 bytes [2.00 TB]
Sector Size:      512 bytes logical/physical
ATA Version is:   8
ATA Standard is:  ATA-8-ACS revision 4

These are from the same manufacturer!  Interestingly, the larger drive 
is actually the older one!

Is the "standardization" not a fixed value but a minimum?  If so, what 
is that actual minimum?  If it's an actual 2 terabyte (2x10^12), then I 
suppose they're both technically over, but that means that we can't just 
simply create partitions that fill the space and expect to be able to 
transfer them later. :-(

Cheers,
Tudor.

Re: Aren't 2TB+ disk sizes supposed to be standardized?

[Mikael Abrahamsson]

On Fri, 5 Jul 2013, Tudor Holton wrote:

> These are from the same manufacturer!  Interestingly, the larger drive is 
> actually the older one!

I checked my drives, and all my 2TB drives are:

User Capacity:    2 000 398 934 016 bytes [2,00 TB]

> Is the "standardization" not a fixed value but a minimum?  If so, what 
> is that actual minimum?  If it's an actual 2 terabyte (2x10^12), then I 
> suppose they're both technically over, but that means that we can't just 
> simply create partitions that fill the space and expect to be able to 
> transfer them later. :-(

Are you sure smartctl actually reads from the drive and doesn't query the 
controller? Only thing I can think of is that sdc sits on a controller 
that puts in a superblock between the OS and the drive, and thus truncates 
the size you can use.

2000397852160-2000398934016
-1081856
1081856/4096
264.125

However, it's a really odd size difference.

-- 
Mikael Abrahamsson    email: swmike@swm.pp.se

Re: Aren't 2TB+ disk sizes supposed to be standardized?

[Kai Stian Olstad]

On 07/05/2013 07:19 AM, Tudor Holton wrote:
> $ sudo fdisk -l
> Disk /dev/sdc: 2000.4 GB, 2000397852160 bytes
> 255 heads, 63 sectors/track, 243201 cylinders, total 3907027055 sectors
> 
> $ sudo smartctl -a /dev/sdc
> Model Family:     Seagate Barracuda (SATA 3Gb/s, 4K Sectors)
> Device Model:     ST2000DM001-1CH164
> Firmware Version: CC43
> User Capacity:    2,000,397,852,160 bytes [2.00 TB]

According to the product manual this disk has guaranteed sectors count
of 3,907,029,168 (one sector counts as 512 bytes).

3,907,029,168 * 512 = 2,000,398,934,016 bytes

As Mikael wrote is probably your controller.

-- 
Kai Stian Olstad