[linux-lvm] Problem while creating a Logical Volume on a Multipath Lun

[Sameer Halgatti]

Hi,
I am facing problem while creating a Logical Volume on a Multipath Lun.
There are 4 paths to a LUN. The corresponding scsi devices are /dev/sdg, /dev/sdu, /dev/sdba, /dev/sdbj.

1. Initially there were no PVs, VGs and LVs.
[root at PC-P31211 root]# pvscan
pvscan -- reading all physical volumes (this may take a while...)
pvscan -- ERROR "pv_read(): read" reading physical volumes
 
[root at PC-P31211 root]# vgscan
vgscan -- reading all physical volumes (this may take a while...)
vgscan -- "/etc/lvmtab" and "/etc/lvmtab.d" successfully created
vgscan -- WARNING: This program does not do a VGDA backup of your volume group
 
[root at PC-P31211 root]# lvscan
lvscan -- no volume groups found

2. Then I created a PV on /dev/sdg1. (I had already created partitions of sdg)
[root at PC-P31211 root]# pvcreate /dev/sdg1
pvcreate -- physical volume "/dev/sdg1" successfully created
The o/p of pvscan is as follows,
[root at PC-P31211 root]# pvscan
pvscan -- reading all physical volumes (this may take a while...)
pvscan -- inactive PV "/dev/sdg1"  is in no VG  [402.61 MB]
pvscan -- inactive PV "/dev/sdu1"  is in no VG  [402.61 MB]
pvscan -- inactive PV "/dev/sdba1" is in no VG  [402.61 MB]
pvscan -- inactive PV "/dev/sdbj1" is in no VG  [402.61 MB]
pvscan -- total: 4 [1.57 GB] / in use: 0 [0] / in no VG: 4 [1.57 GB]
Here u can notice that even though I have created PV on sdg, pvscan shows all the scsi devices which are pointing to the same LUN.

3. Then I created a VG on PV /dev/sdg1
[root at PC-P31211 root]# vgcreate test_vg /dev/sdg1
vgcreate -- INFO: using default physical extent size 4 MB
vgcreate -- INFO: maximum logical volume size is 255.99 Gigabyte
vgcreate -- doing automatic backup of volume group "test_vg"
vgcreate -- volume group "test_vg" successfully created and activated
The o/p of vgscan & pvscan is as follows,
[root at PC-P31211 root]# vgscan
vgscan -- reading all physical volumes (this may take a while...)
vgscan -- found active volume group "test_vg"
vgscan -- "/etc/lvmtab" and "/etc/lvmtab.d" successfully created
vgscan -- WARNING: This program does not do a VGDA backup of your volume group
[root at PC-P31211 root]# pvscan
pvscan -- reading all physical volumes (this may take a while...)
pvscan -- ACTIVE   PV "/dev/sdg1"  of VG "test_vg" [396 MB / 396 MB free]
pvscan -- inactive PV "/dev/sdu1"  of VG "test_vg" [396 MB / 396 MB free]
pvscan -- inactive PV "/dev/sdba1" of VG "test_vg" [396 MB / 396 MB free]
pvscan -- inactive PV "/dev/sdbj1" of VG "test_vg" [396 MB / 396 MB free]
pvscan -- total: 4 [1.57 GB] / in use: 4 [1.57 GB] / in no VG: 0 [0]

4. Then I tried to create LV on "test_vg". But that gave me error.
[root at PC-P31211 root]# lvcreate -L 50 -n test_lv test_vg
lvcreate -- rounding size up to physical extent boundary
lvcreate -- ERROR "No such device or address" creating VGDA for "/dev/test_vg/te
st_lv" in kernel

Also see the results of lvscan & lvdisplay which are contradictory.
[root at PC-P31211 root]# lvscan
lvscan -- ACTIVE            "/dev/test_vg/test_lv" [52 MB]
lvscan -- 1 logical volumes with 52 MB total in 1 volume group
lvscan -- 1 active logical volumes

[root at PC-P31211 root]# lvdisplay /dev/test_vg/test_lv
lvdisplay -- logical volume "/dev/test_vg/test_lv" doesn't exist

Can any body help me to solve this problem???

Somebody suggested me a solution...
a. Deactivate VG
b. Run vgscan
c. Activate VG
d. Create LV.
I followed these step. The o/p is given below.
[root at PC-P31211 root]# vgchange -an
vgchange -- volume group "test_vg" successfully deactivated
 
[root at PC-P31211 root]# vgscan
vgscan -- reading all physical volumes (this may take a while...)
vgscan -- found inactive volume group "test_vg"
vgscan -- "/etc/lvmtab" and "/etc/lvmtab.d" successfully created
vgscan -- WARNING: This program does not do a VGDA backup of your volume group
 
[root at PC-P31211 root]# vgchange -ay
vgchange -- volume group "test_vg" successfully activated
 
[root at PC-P31211 root]# pvscan
pvscan -- reading all physical volumes (this may take a while...)
pvscan -- inactive PV "/dev/sdg1"  of VG "test_vg" [396 MB / 396 MB free]
pvscan -- inactive PV "/dev/sdu1"  of VG "test_vg" [396 MB / 396 MB free]
pvscan -- inactive PV "/dev/sdba1" of VG "test_vg" [396 MB / 396 MB free]
pvscan -- ACTIVE   PV "/dev/sdbj1" of VG "test_vg" [396 MB / 396 MB free]
pvscan -- total: 4 [1.57 GB] / in use: 4 [1.57 GB] / in no VG: 0 [0]
 
[root at PC-P31211 root]# lvcreate -L 50 -n test_lv test_vg
lvcreate -- rounding size up to physical extent boundary
lvcreate -- doing automatic backup of "test_vg"
lvcreate -- logical volume "/dev/test_vg/test_lv" successfully created
 
[root at PC-P31211 root]# lvscan
lvscan -- ACTIVE            "/dev/test_vg/test_lv" [52 MB]
lvscan -- 1 logical volumes with 52 MB total in 1 volume group
lvscan -- 1 active logical volumes
 
[root at PC-P31211 root]# lvdisplay /dev/test_vg/test_lv
--- Logical volume ---
LV Name                /dev/test_vg/test_lv
VG Name                test_vg
LV Write Access        read/write
LV Status              available
LV #                   1
# open                 0
LV Size                52 MB
Current LE             13
Allocated LE           13
Allocation             next free
Read ahead sectors     120
Block device           58:0

This apporach helped me to create the Logical Volume. But it does not fulfill my requirement. Here initially I had created VG on sdg1, but after doing (vgchange -an, vgscan, vgchage -ay) that VG got shifted on sdbj. And hence LV will also be created on this LV. But I want LV to be created on sdj only. Is there any solution to my problem???

Regards,
Sameer Halgatti

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