moving a volume group to new disks

[mmartini]

hello

i have to move and entire vg to new disks (anothe storage)using lvm. which is the safest way? No downtime is permitted...
Mirroring?
thank you!

[James R. Ferguson]

Hi:

Yes, without downtime, leveraging LVM mirroring is going to be about your only choice. Mirroring is certainly very safe although the operation of synchronization can be time-consuming and resource-consumptive.

Of course, mirroring occurs at the logical volume level, so you will have to perform the replication a logical-volume at a time.

Depending upon your configuration, you might want to setup physical volume groups or you might want to explicitly specify the pv_path involved in each mirror operation ('lvextend'). An '/etc/lvmpvg' file defining physical volume groups can be built at any time. That is, you can create it now, even if it didn't exist before.

Examine the manpages for 'lvextend(1M)' and 'lvmpvg(4)' for more information.

Regards!

...JRF...

[mmartini]

thank you James

just to verify the procedure...after i have a mirror of all the volumes on the new disks, i just have to lvreduce the old volumes and vgreduce the old disk? nothing else to do?
thank you

[James R. Ferguson · Accepted solution]

Hi (again) mmartini:

You wrote:

> after i have a mirror of all the volumes on the new disks, i just have to lvreduce the old volumes and vgreduce the old disk?

No, after mirroring all of the logical volumes from the old to the new disks, to remove the *old* mirror copies, you do:

# lvextend -m 0 /dev/vgNN/lvolX /dev/dsk/cXtYdZ

...where cXtYdZ represents the *old* physical volume that you will be eliminating.

Then, when cXtYdZ is totally devoid of any inuse extents, you can 'vgreduce' it from the volume group.

Overall, the elimination of the *old* structures is the reverse of creating the *new* ones. That is, you add the new physical volumes with 'vgextend', and follow that with 'lvextend -m 1 ...' to build a mirror of each logical volume. When done, you do 'lvextend -m 0 ...' to eliminate the old mirror and then 'vgreduce' to eliminate the old physical volume.

Regards!

...JRF...

[mmartini]

thank you James. I's clear now.

[Doug O'Leary]

Hey;

Also be aware that when you add the new disks to the system, they must be of similar size to the older disks. For instance, if your old disks are 8 gigs and your new disks are 72 gigs; you'll only see about 10-12 gigs of the new disks. The rest of the space will be wasted.

Doug