Message by hpSMC

[Prashant Zanwar_4]

Hi,
I have ran a program given by HP called HPSMC which has generated several messages for me. One of the message out of this is
"Mirrored Logical Volumes have been implemented without Physical Volume Groups"
What this implies, I am sure it is speaking of PVG policy. But how to know which volume group is missing it and then how to change the policy. Is it possible using vgchange and does it requires de-activation of volume.
Pls advise
Thanks
Prashant

[Sundar_7 · Accepted solution]

Prashant,

Try this

vgdisplay -v | grep "LV Name" | awk '{print $3}' | while read LV
do
echo "$LV \c"; lvdisplay $LV | egrep "Mirror|Allocation"
done

This will tell you all the logical volume's mirror status and the allocation policy.

Figure out the ones that have mirror copies and with allocation policy other than "PVG Strict"

If the allocation policy is not strict or PVG-Strict then chances are that your logical volumes could have been mirroed to the same physical volume,

This is not preferred since if you lose the physical volume, you lose both the primary and mirror copies.

Sure, you can change the allocation policy, but you have to remove the mirrors first

1) Figure out the logical volumes

2) lvreduce -m 0 /dev/vgXx/lvolYY

Reduce the mirrors

3) lvchange -s g /dev/vgXX/lvolYY

4) Edit /etc/lvmpvg and create PVGs

5) lvextend -m 1 /dev/vgXX/lvolYY

Sundar.

[Prashant Zanwar_4]

Hey just something ahead of this.
What about the root volume group. Can I do the same for root VG also. And if so, do I need to do all boot update on the root mirror disk again. Please reply
Thanks and regards
Prashant

[Sundar_7]

If the mirror disk is already bootable (created with pvcreate -B and mkboot) then you dont have to execute the commands that affect the BDRA of the mirror disk

For roor VG

1) Reduce the mirrors

2) execute lvchange and change the allocation policy

3) execute lvextend and re-mirror the lvs

4) lvlnboot -R

4) confirm with lvlnboot -v

-- Sundar

[Prashant Zanwar_4]

I have checked as advised and allocation policy is strict for all LV's. Do I still need to change it to PVG strict? Please advise
Prashant

[Sundar_7]

Strict allocation policy is good enough in most of the cases.

The difference is ...

With PVG strict, you need to create PVG groups in /etc/lvmpvg with one PVG listing the disks attached to one controller with the another PVG listing the disks attached to a different controller.

Now if you enable PVG strict and mirror the LV, the copies of the LV will be in disks that are attached to two different controllers.

This way you are eliminating the single point of failure of the controllers.

If the primary and mirror disks you have are attached to the same controller then there is no difference between strict and PVG-strict as far as mirroring is concerned.

[Prashant Zanwar_4]

Thanks a lot for all replies.
I have to figure out now when can I do it.
Rgdz
Prashant