disk capacity discrepancy: is it 1000 versus 1024?
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Quoted 15 lines · Maurice Volaski
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.
Quoted 6 lines
other keywords: gigabinarybytes, gibibytes, Gi, terabinarybytes, tebibytes, Ti. --
Maurice Volaski, [email protected]
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
Signature · 3 lines
Greg Freemyer The Norcross Group Forensics for the 21st Century
Quoted 37 lines · Greg Freemyer
Quoted 15 lines · Maurice Volaski
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.
Quoted 6 lines
other keywords: gigabinarybytes, gibibytes, Gi, terabinarybytes, tebibytes, Ti. --
Maurice Volaski, [email protected]
Computing Support, Rose F. Kennedy Center
Albert Einstein College of Medicine of Yeshiva UniversityAs 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 BytesOr 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.
Quoted 9 lines
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
Maurice,
I forgot to add that disk drive manufactures have been selling disks by the GB for years, not the GiB. Thus your 400 GB disk drive is most likely about 373 GiB. (I used a calculator).
One way to tell for sure is to get the number of sectors and multiply it out. Sectors are typically 512 bytes. You can typically see the sector count or the paper label of newer drives, or with standard ide disks in /proc/ide/hdx/capacity.
Greg
Signature · 3 lines
Greg Freemyer The Norcross Group Forensics for the 21st Century
Quoted 57 lines
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Greg Freemyer
Sent: Sunday, 15 May 2005 7:42 AM
To: LVM general discussion and development
Subject: Re: [linux-lvm] disk capacity discrepancy: is it 1000 versus 1024?Quoted 3 lines · Greg Freemyer
Quoted 2 lines · Maurice Volaski
I originally had a hardware RAID with fourteen 400 GB drives of usable capacity (Hitachi 7K400) . That's 5600 GB
altogether. That's
Quoted 3 lines
Quoted 3 lines
what both fdisk and df report (filesystem was ext3).
When I instead created an LVM2 physical volume on the
device, I get
Quoted 3 lines
Quoted 3 lines
just 5.09 TB.
Is LVM eating several hundreds gigabytes of space or is
it the case
Quoted 1 line
Quoted 1 line
that LVM uses terminology in a strict multiply by 1024
fashion versus
Quoted 1 line
Quoted 1 line
everything else, which is multiplying by 1000. In that
case, I guess
Quoted 6 lines
Quoted 6 lines
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.
Quoted 15 lines
Quoted 5 lines
--
Maurice Volaski, [email protected]
Computing Support, Rose F. Kennedy Center
Albert Einstein College of Medicine of Yeshiva UniversityAs 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 BytesQuoted 7 lines
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?"Maurice,
Quoted 9 lines
I forgot to add that disk drive manufactures have been selling disks by the GB for years, not the GiB. Thus your 400 GB disk drive is most likely about 373 GiB. (I used a calculator).
One way to tell for sure is to get the number of sectors and multiply it out. Sectors are typically 512 bytes. You can typically see the sector count or the paper label of newer drives, or with standard ide disks in
/proc/ide/hdx/capacity.
Although Greg has bascially done the maths, it works out exactly right as 5.09TiB
i.e. 14 * 400 * 10^9 = 5600 * 10^9 = 5.6 * 10^12 TB
In TiB
(5.6 * 10 ^12) / (1024 * 1024 * 1024 * 1024) = 5.09 TiB which is exactly what you are seeing.
I would guess LVM is simply reporting TiB with the suffix TB since the whole Gibi, Tibi etc thing is yet to completely take off and not everyone is using it.
It starts getting a bit rough when you lose 500GB due to 1024 vs 1000.
CH