What happens when vgimport attempts to import physical volume in wrong order?

[Jack C. Mahaffey]

What happens when vgimport attempts to import physical volumes in wrong order?

jack...

[A. Clay Stephenson · Accepted solution]

Hi Jack,

It works fine. If you are concerned about splitting I/O across both your external paths, see my response to your earlier posting.

[S.K. Chan]

I suppose nothing will happen. If you use -s option in the vgimport command, it'll scan the system backplane in sequence and sometimes one is discover first than the other and hence PVs can be in wrong order.

[pap]

Nothing happens....as long as your volume group is imported in the same vg disks.

[Roger Baptiste]

Hi,

It works just fine. The only hitch (if it is considered one) is that the load balancing across pv paths may not be the way you desire it be.

HTH
raj

[Mark van Hassel]

Hi,

When you want to make sure the PVs are in a particular order because of load balancing just specify them in the vgimport command:

vgimport vgname PV1 PV2 PV3 PV4 ...


HtH,

Mark

[Domenico_5]

hi jack

It works correctly, i have checked it now.

But, how the other guys say, the balancing may be not the correct way, moreover if the volume group is used in a cluster with cluster lock, in syslog file you can read "unable to find cluster lock".

In this case you must restore the correct order.

p.s. vgimport -s means sherable and not scan (from man page)

hi to all

[Jack C. Mahaffey]

Thanks all...

I was interested if there were any issues of corrupting the volume group which leads me to two more questions.

What happens if:
1- One of the physical volumes is missed in the vgimport? For example, my volume group has 4 physical volumes and I miss one of the physical volumes on the vgimport. Asuume there are no alternate paths for this dicussion.

2- A physical volume that belongs to another volume group is incorrectly included in the vgimport? It's possible to 'fat-finger' a device name.



Jack...

[S.K. Chan]

1) It will import it anyway but when you try to activate the vg (# vgchange -a y ) you would get an error that says something like .."cannot open PV.."

2) It'll fail, vgimport behaves like vgcreate, meaning it'll scan the PVs for VG information and it it finds a PV that belong to another VG it'll tell you it cannot proceed.

[Helen French]

Hi,

1) The vgimport command will work. However you will have trouble activating the VG. In case of a mirror/disk, you can activate the VG without quorum check (-q). See man pages of vgchange.

2) In this case, the vgimport will give you error. When executing vgimport command, the system will check the VG reserved area of all disks for volume group information; and if not matched, then it will fail.

HTH,
Shiju

[Domenico_5]

hi jack

do you want to crash your server?

1) if you not include a disk, you lose the data on it but vgimport end correctly, LVM tell you only the number of disk used and the number of disk included

2) if you include a wrong disk used in another vg LVM respond:"The Physical Volumes specified on the command line do not belong to the same Volume Group"


bye

[Jack C. Mahaffey]

Nope... Don't want to crash the server. Just want to know a little more about the internals so that I know the impacts of messing up. I want to be able to explain the consequences to junior administrations of impacts of doing the wrong thing. Believe me, I've had my turn messing up many times.

:)

Thanks for the feedback...