[linux-lvm] lvreduce nightmare

tariq wali ganaiwali at gmail.com
Sun May 20 08:59:56 UTC 2012

Hi Andy,

Thanks for the mail.

I am not sure if reducing by lvreduce alone is safe and will actually
reduce the underneath file system also, look at this sequence ..

lvcreate -n test -L10G vg0

df -h /test/
Filesystem                 Size  Used   Avail Use% Mounted on
/dev/mapper/vg0-test  9.9G  151M  9.2G   2% /test

created some pseudo 2GB files with dd and /test now is

df -h
Filesystem                Size  Used   *Avail* Use% Mounted on
/dev/mapper/vg0-test  9.9G  2.2G  *7.2G*  24% /test

lvreduce -L -1G -n /dev/vg0/test
LV   VG   Attr   LSize Origin Snap%  Move Log Copy%  Convert
test vg0  -wi-a- 9.00G

mount /dev/vg0/test /test/
df -h
Filesystem                 Size  Used  *Avail* Use% Mounted on
/dev/mapper/vg0-test  9.9G  2.2G  *7.2G*  24% /test

you see after lvreduce 1G and mount /test again , it still shows */test as
7.2G* while as it should be *6.2G*


On Sun, May 20, 2012 at 4:44 AM, Andy Smith <andy at strugglers.net> wrote:

> Hi tariq,
> On Fri, May 18, 2012 at 07:43:40PM +0530, tariq wali wrote:
> > so to i guess to do this right i should have
> >
> > resize2fs /dev/vg0/data 1.6T or (1600G)
> >
> > and then lvreduce -n data -L 100G /dev/vg0/data ( to reduce the lvm by
> 100
> > )
> I believe that will also reduce the LV *to* 100G. You want:
> # lvreduce -n data -L-100G
> if you want to reduce it *by* 100G.
> Nothing like FS/LV shrinking to keep you on your toes..
> Cheers,
> Andy
> --
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*Tariq Wali.*
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