Extending volume group

 
Jim Doddery
New Member

Extending volume group

From what I gather....
"BACKUP, BLOW AWAY VG, RECREATE VG, RESTORE"
is the necessary means to increase Max PE per PV.

Has anyone ever done this before? Apparently, I need to perform this and I've never done this before, so I'm more than a little intimidated.

Thank You
5 REPLIES 5
James R. Ferguson
Acclaimed Contributor

Re: Extending volume group

Hi Jim:

Yes, that is the means to increase a volume group's 'max_pe' or 'max_pv' or 'pe_size' or 'max-lv'.

The easy approach is to backup your filesystems and then:

# vgchange -a n vgXX
# vgexport vgXX

This quickly eliminates the volume group and all its logical volumes. You will need to do :

# pvcreate -f

...to overwrite the LVM header since LVM will ever-so-helpfully try to warn you that LVM information still exists on the physical disks (it does).

Now, follow the normal steps ('mknod', 'pvcreate', 'vgcreate', 'lvcreate' and build a new volume group and restore your data.

Regards!

...JRF...
A. Clay Stephenson
Acclaimed Contributor

Re: Extending volume group

Yep, that's how you do it. I would add a step after backup, verify backup. If that's done no matter how badly you screw up then no lasting damage will be done. It's one of God's little jokes, it you have a known good backup then you don't need it; if you don't ... .

There is another option. You can add additional disks (LUN's) of the same size as the largest existing PV to your VG. You can even add larger disks if you are willing to allow some of the space to go unused.

If you are unfamiliar with the process; other than the backups and verify, every needed step can be done under SAM. Backups and restores can also be done using SAM but this is one area where I would absolutely know what commands and what options are used. Your fastest free backup/restore tool is fbackup/frecover so make youreself very familiar with those commands to the point of doing some non-critical backups and restores before doing the real thing.
If it ain't broke, I can fix that.
A. Clay Stephenson
Acclaimed Contributor

Re: Extending volume group

By the way, I assume this is non vg00 because that add's a whole new level of complexity to the task because now we are into Ingite/UX.
If it ain't broke, I can fix that.
Jim Doddery
New Member

Re: Extending volume group

Thanks, gentlemen.

It's actually "vg08", and it houses Informix dataspaces. I'm currently holding down the fort until a new guy starts in a few weeks.

I'll let you know what happens.

Thanks again
A. Clay Stephenson
Acclaimed Contributor

Re: Extending volume group

There may be a problem. If your Informix data are stored as raw devices then the standard backup tools are not going to work; the only UNIX tool that can do this is dd and there is essentially no way to verify the data other than a cksum. You need to look at the Informix backup tools (e.g. ontape).
If it ain't broke, I can fix that.