Map lvm volume to Physical volume - linux

Question

lsblk provides output in this fornat:
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sr0 11:0 1 1024M 0 rom
sda 8:0 0 300G 0 disk
sda1 8:1 0 500M 0 part /boot
sda2 8:2 0 299.5G 0 part
vg_data1-lv_root (dm-0) 253:0 0 50G 0 lvm /
vg_data2-lv_swap (dm-1) 253:1 0 7.7G 0 lvm [SWAP]
vg_data3-LogVol04 (dm-2) 253:2 0 46.5G 0 lvm
vg_data4-LogVol03 (dm-3) 253:3 0 97.7G 0 lvm /map1
vg_data5-LogVol02 (dm-4) 253:4 0 97.7G 0 lvm /map2
sdb 8:16 0 50G 0 disk
for a mounted volume say /map1 how do i directly get the physical volume associated with it. Is there any direct command to fetch the information?

Answer 1

There is no direct command to show that information for a mount. You can run
lvdisplay -m
Which will show which physical volumes are currently being used by the logical volume.
Remember, thought, that there is no such thing as a direct association between a logical volume and a physical volume. Logical volumes are associated with volume groups. Volume groups have a pool of physical volumes over which they can distribute any volume group. If you always want to know that a given lv is on a given pv, you have to restrict the vg to only having that one pv. That rather misses the point. You can use pvmove to push extents off a pv (sometimes useful for maintenance) but you can't stop new extents being created on it if logical volumes are extended or created.
As to why there is no such potentially useful command...
LVM is not ZFS. ZFS is a complete storage and filesystem management system, managing both storage (at several levels of abstraction) and the mounting of filesystems. LVM, in contrast, is just one layer of the Linux Virtual File System. It provides a layer of abstraction on top of physical storage devices and makes no assumption about how the logical volumes are used.

Answer 2

Leaving the grep/awk/cut/whatever to you, this will show which PVs each LV actually uses:
lvs -o +devices
You'll get a separate line for each PV used by a given LV, so if an LV has extents on three PVs you will see three lines for that LV. The PV device node path is followed by the starting extent(I think) of the data on that PV in parentheses.

Answer 3

I need to emphasize that there is no direct relation between a mountpoint (logical volume) and a physical volume in LVM. This is one of its design goals.
However you can traverse the associations between the logical volume, the volume group and physical volumes assigned to that group. However this only tells you: The data is stored on one of those physical volumes, but not where exactly.
I couldn't find a command which can produce the output directly. However you can tinker something using mount, lvdisplay, vgdisplay and awk|sed:
mp=/mnt vgdisplay -v $(lvdisplay $(mount | awk -vmp="$mp" '$3==mp{print $1}') | awk '/VG Name/{print $3}')
I'm using the environment variable mp to pass the mount point to the command. (You need to execute the command as root or using sudo)
For my test-scenario it outputs:
...
--- Volume group ---
VG Name vg1
System ID
Format lvm2
Metadata Areas 2
Metadata Sequence No 2
VG Access read/write
VG Status resizable
...
VG Size 992.00 MiB
PE Size 4.00 MiB
Total PE 248
Alloc PE / Size 125 / 500.00 MiB
Free PE / Size 123 / 492.00 MiB
VG UUID VfOdHF-UR1K-91Wk-DP4h-zl3A-4UUk-iB90N7
--- Logical volume ---
LV Path /dev/vg1/testlv
LV Name testlv
VG Name vg1
LV UUID P0rgsf-qPcw-diji-YUxx-HvZV-LOe0-Iq0TQz
...
Block device 252:0
--- Physical volumes ---
PV Name /dev/loop0
PV UUID Qwijfr-pxt3-qcQW-jl8q-Q6Uj-em1f-AVXd1L
PV Status allocatable
Total PE / Free PE 124 / 0
PV Name /dev/loop1
PV UUID sWFfXp-lpHv-eoUI-KZhj-gC06-jfwE-pe0oU2
PV Status allocatable
Total PE / Free PE 124 / 123
If you only want to display the physical volumes you might pipe the results of the above command to sed:
above command | sed -n '/--- Physical volumes ---/,$p'

Answer 4

dev=$(df /map1 | tail -n 1|awk '{print $1}')
echo $dev | grep -q ^/dev/mapper && lvdisplay -m $dev 2>/dev/null | awk '/Physical volume/{print $3}' || echo $dev