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Re: [linux-lvm] disk capacity discrepancy: is it 1000 versus 1024?



On 5/14/05, Maurice Volaski wrote:
> I originally had a hardware RAID with fourteen 400 GB drives of
> usable capacity (Hitachi 7K400) . That's 5600 GB altogether. That's
> what both fdisk and df report (filesystem was ext3).
> 
> When I instead created an LVM2 physical volume on the device, I get
> just 5.09 TB.
> 
> Is LVM eating several hundreds gigabytes of space or is it the case
> that LVM uses terminology in a strict multiply by 1024 fashion versus
> everything else, which is multiplying by 1000. In that case, I guess
> the drives aren't really 400 GBs. :-(
> 
> However, it appears that parameters passed to LVM commands are
> interpreted using x1000, not x1024.
> 
> other keywords: gigabinarybytes, gibibytes, Gi, terabinarybytes, tebibytes, Ti.
> --
> 
> Maurice Volaski, mvolaski aecom yu edu
> Computing Support, Rose F. Kennedy Center
> Albert Einstein College of Medicine of Yeshiva University

As Maurice implies NIST is making an effort (however small) to
standardize GB as 1000 * 1000 * 1000 bytes.

See http://physics.nist.gov/cuu/Units/binary.html

So per NIST:
GB = Gigabyte = 1,000 * 1,000 * 1,000 Bytes
GiB = Gibibyte  = 1,024 * 1,024 * 1,024 Bytes

Or for Maurice TB vs. TiB

BTW, the difference between TB and TiB is almost 10% so this has a
very user observable effect and would explain Maurice's discrepancy.

So if I understand Maurice's question, it becomes:
   "Is LVM reporting TiB units with a TB designation?"

Greg
-- 
Greg Freemyer
The Norcross Group
Forensics for the 21st Century


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