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#1 2008-12-04 18:14:28

kludge
Member
Registered: 2008-08-03
Posts: 294

LVM 6GB smaller than partition... Why?!?

i finally managed to get my system moved over to lvm2 so i won't ever have to manually move, grow, shrink, etc. partitions ever again.

however, my paritition is 120 GB:

    Name        Flags      Part Type  FS Type          [Label]        Size (MB)
 ------------------------------------------------------------------------------
    sda1        Boot        Primary   Linux ext3                         131.61 
    sda2                    Primary   Linux LVM                       122885.69

and yet the volume group only has 114 GB available:

  --- Volume group ---
  VG Name               lvg1
  System ID             
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  6
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                5
  Open LV               4
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               114.44 GB
  PE Size               4.00 MB
  Total PE              29297
  Alloc PE / Size       17408 / 68.00 GB
  Free  PE / Size       11889 / 46.44 GB
  VG UUID               blargh-blah-foob-arrr-stuff-junk-blargh

what gives?  where'd those 6 gigs go?


[23:00:16]    dr_kludge | i want to invent an olfactory human-computer interface, integrate it into the web standards, then produce my own forked browser.
[23:00:32]    dr_kludge | can you guess what i'd call it?
[23:01:16]    dr_kludge | nosilla.
[23:01:32]    dr_kludge | i really should be going to bed.  i'm giggling madly about that.

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#2 2008-12-05 01:56:19

iBertus
Member
From: Greenville, NC
Registered: 2004-11-04
Posts: 2,228

Re: LVM 6GB smaller than partition... Why?!?

Could this be another GiB vs GB conversion issue? I don't think the numbers look right for that, as 122885/1024 = 120 and not 114. Strange. Not as strange as whatever the hell that thing is in your avatar, but strange.

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#3 2008-12-05 02:54:05

kludge
Member
Registered: 2008-08-03
Posts: 294

Re: LVM 6GB smaller than partition... Why?!?

hmmm...

114.4 * 1024 * 1024 * 1024 = 122836064665.6 Bytes

122885.69 * 1024 * 1024 = 128854985277.44 Bytes

128854985277.44 - 122836064665.6 = 6018920611.84 Bytes difference

6018920611.84 / 1024 / 1024 / 1024 = 5.605556640625 GB difference

i know hardware manufacturers' marketing departments take advantage of the GiB/GB difference, but i'm going to hazard a guess that the authors of lvm2 and cfdisk don't.

i also know that partition tables, block-device encryption, and logical-volume management all entail some disk-space overhead, but

5.605556640625 / ( 122885.69 / 1024 ) = ~4.67108 %

5%.  does that seem suspicious?  i really don't know.

p.s.: that thing is a holoprosencephallic piglet.  it's not my usual avatar, but i couldn't find that file after the harddrive switch.  i like it 'cuz it's hideous and adorable all at once, kind of like a good kludge.


[23:00:16]    dr_kludge | i want to invent an olfactory human-computer interface, integrate it into the web standards, then produce my own forked browser.
[23:00:32]    dr_kludge | can you guess what i'd call it?
[23:01:16]    dr_kludge | nosilla.
[23:01:32]    dr_kludge | i really should be going to bed.  i'm giggling madly about that.

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#4 2009-10-24 13:49:57

fede
Member
Registered: 2007-06-29
Posts: 126

Re: LVM 6GB smaller than partition... Why?!?

I suppose it's too late to care about this, but it is said in the wiki that ext3 reserves 5% of space for "special reasons". See http://wiki.archlinux.org/index.php/Ext … stem_Space

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