[linux-lvm] Only 4MB of space on a 1GB file mounted in loopback

[Ray Morris]

> but I end up with a file of 4MB, do you have any idea what went wrong?

You end up with a logical volume of 4 MB.  Let's look at where you
created that logical volume:

> lvcreate -i1 -l 1 -n testvol testgroup

"-l 1" sets the size as 1 logical extent, which is 4MB by default.

   Note that if you are using version 1 of LVM, or using
version 1 style metadata with LVM2, a 4MB extent size limits
the size of logical volumes you can create to 255GB (256GB?).
--
Ray Morris
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On 07/07/2010 08:32:49 AM, Benjamin Henrion wrote:
> Hi,
> 
> I have setup some LVM volume to test on a loopback file of 1GB, but I
> end up with a file of 4MB, do you have any idea what went wrong?:
> 
> ===========================================================
> root at buzek /home/zoobab [22]# dd if=/dev/zero of=1G.img bs=1G count=1
> 1+0 records in
> 1+0 records out
> 1073741824 bytes (1.1 GB) copied, 13.6855 s, 78.5 MB/s
> root at buzek /home/zoobab [23]# losetup -f
> /dev/loop5
> root at buzek /home/zoobab [24]# losetup /dev/loop5 1G.img
> root at buzek /home/zoobab [25]#  pvcreate /dev/loop5
>   Physical volume "/dev/loop5" successfully created
> root at buzek /home/zoobab [26]# vgcreate testgroup /dev/loop5
>   Volume group "testgroup" successfully created
> root at buzek /home/zoobab [27]# lvcreate -i1 -l 1 -n testvol testgroup
>   Redundant stripes argument: default is 1
>   Logical volume "testvol" created
> root at buzek /home/zoobab [28]# mkfs.ext3 /dev/testgroup/testvol
> mke2fs 1.41.9 (22-Aug-2009)
> Filesystem label=
> OS type: Linux
> Block size=1024 (log=0)
> Fragment size=1024 (log=0)
> 1024 inodes, 4096 blocks
> 204 blocks (4.98%) reserved for the super user
> First data block=1
> Maximum filesystem blocks=4194304
> 1 block group
> 8192 blocks per group, 8192 fragments per group
> 1024 inodes per group
> Writing inode tables: done
> Creating journal (1024 blocks): done
> Writing superblocks and filesystem accounting information: done
> This filesystem will be automatically checked every 31 mounts or
> 180 days, whichever comes first.  Use tune2fs -c or -i to override.
> root at buzek /home/zoobab [29]# mount /dev/testgroup/testvol  /mnt
> root at buzek /home/zoobab [30]# cd /mnt
> root at buzek /mnt [31]# df -lha
> Filesystem            Size  Used Avail Use% Mounted on
> /dev/sda1              57G   46G  7.7G  86% /
> proc                     0     0     0   -  /proc
> none                     0     0     0   -  /sys
> none                     0     0     0   -  /sys/fs/fuse/connections
> none                     0     0     0   -  /sys/kernel/debug
> none                     0     0     0   -  /sys/kernel/security
> udev                  1.4G  260K  1.4G   1% /dev
> none                     0     0     0   -  /dev/pts
> none                  1.4G  900K  1.4G   1% /dev/shm
> none                  1.4G  124K  1.4G   1% /var/run
> none                  1.4G     0  1.4G   0% /var/lock
> none                  1.4G     0  1.4G   0% /lib/init/rw
> binfmt_misc              0     0     0   -  /proc/sys/fs/binfmt_misc
> gvfs-fuse-daemon      0.0K  0.0K  0.0K   -  /home/zoobab/.gvfs
> /dev/mapper/testgroup-testvol
>                       3.9M  1.1M  2.7M  29% /mnt
> root at buzek /mnt [32]#
> ===========================================================
> 
> --
> Benjamin Henrion <bhenrion at ffii.org>
> FFII Brussels - +32-484-566109 - +32-2-4148403
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> 
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>