LVM Question

[Notts_sys]

Dear All,

We are having this issue with LVM and it looks like we are not able to see full capacity of LUNs presented to the server.

We presented 2 X 2 TB of Luns to this box (sda and sdb), then created partitions sda1 and sdb1 of 2TB capacity each and added them to the volume group. Volume Group info as below. From the display below, we can see that the disks /dev/sda1 and /dev/sda2 both have 476835 PE so around 2TB, thats fine. The VG has total PE of 953670, fine too. but then why the VG Size is only 3.64 TB. As per my calculation it should be 953670 x 4.00 MB = 3814680 (3.8 TB), i wonder why it only shows 3.64 TB ? Please comment.

The system in question is openSUSE 10.2 (i586), LVM: lvm2-2.02.13-10.2



#vgdisplay -v vgBackup | more
Using volume group(s) on command line
Finding volume group "vgBackup"
--- Volume group ---
VG Name vgBackup
System ID
Format lvm2
Metadata Areas 2
Metadata Sequence No 5
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 1
Open LV 1
Max PV 0
Cur PV 2
Act PV 2
VG Size 3.64 TB
PE Size 4.00 MB
Total PE 953670
Alloc PE / Size 917504 / 3.50 TB
Free PE / Size 36166 / 141.27 GB
VG UUID 05Wqus-mSip-psJr-jsgS-lmck-nbaw-ydu53r

--- Logical volume ---
LV Name /dev/vgBackup/lvBackup
VG Name vgBackup
LV UUID nPQPwE-gL8S-igJ1-ClUV-kkQB-aK2q-2auuSu
LV Write Access read/write
LV Status available
# open 1
LV Size 3.50 TB
Current LE 917504
Segments 2
Allocation inherit
Read ahead sectors 0
Block device 253:0

--- Physical volumes ---
PV Name /dev/sdb4
PV UUID 3C01SL-QVDq-gs2f-K1kk-0gx1-fg3p-hZRfhi
PV Status allocatable
Total PE / Free PE 476835 / 0

PV Name /dev/sda1
PV UUID 33Enrm-GI0i-OQew-HcbG-OBZM-Qcin-HZy6Nc
PV Status allocatable
Total PE / Free PE 476835 / 36166

[Heironimus · Accepted solution]

Multipliers of 1000 vs. 1024. One of the reasons that "human readable" sizes are often a bad thing for admins.

953670 extents, 4MB/extent = 3814680MB

3814680MB, 1024MB/1GB = 3725.27GB

3725.27GB, 1024GB/1TB = 3.64TB

[Notts_sys]

Thanks.