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Losing 4Gb on Debian LVM?

Hello all,

I'm creating LVM in the following way,

pvcreate /dev/sdc (a virtual disk of 275G)

Quote:

Physical volume "/dev/sdc" successfully created

vgcreate vg_test /dev/sdc

Quote:

Volume group "vg_test" successfully created

lvcreate -n lv_test -l 100%FREE vg_test

Quote:

Logical volume "lv_test" created

Quote:

root@debian:~# pvs
PV VG Fmt Attr PSize PFree
/dev/sdc vg_test lvm2 a-- 275.00g 0

Quote:

root@debian:~# vgs
VG #PV #LV #SN Attr VSize VFree
vg_test 1 1 0 wz--n- 275.00g 0

Quote:

root@debian:~# lvs
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
lv_test vg_test -wi-a----- 275.00g

Then i proceed to create an ext4 fs

mkfs.ext4 /dev/mapper/vg_test-lv_test (everything OK)

and when i mount it...

/dev/mapper/vg_test-lv_test 271G 63M 257G 1% /mnt

Why do i loose 4 GB in the process? is this normal? 4 GB?

It's a LOT of space...

I tried creating a partition of 275GB with the same results..I'm just confused

Cheers!!

df shows space available to non-privileged users. The default is to reserve some space for privileged use. For example:

Code:

 df |grep home

/dev/mapper/vg_ntt2-lv_home

                    205261560  27068952 167742896  14% /home

sudo tune2fs -l /dev/mapper/vg_ntt2-lv_home |grep 'lock count:'

Block count:              52166656

Reserved block count:    2608332

To elaborate on the above 5% is reserved for root when ext2/3/4 filesystems are created. That 5% is not included in the output of the df command so the numbers do not add up. 5% is 13GB.

The difference in the logical volume size versus filesystem size is overhead i.e. metadata. 1.5-2% for ext4 if I remember correctly is normal.

And for a data filesystem, the reserved is pointless - set it to zero using tune2fs.
Note if you plan on running the filesystem really full (95% say) all the time and actively adding/deleting files (all the time) maybe you need some reserved. Never needed to in real life.

You also loose space to support the inode list, block allocation maps, and the journal.

These are necessary to manage files in the filesystem and recover from system crashes/power failures.