HACMP and mirroring

[domi1805]

Hello,
I would like to make a data migration from one external storage system (SAN) to another one, using mirroring to the new LUNs.
But these hosts are running HACMP.
May I use the standard LVM mirroring command like:

"extend vg_name hdisk_name" to add the new disk in the existing VG.
"mklvcopy LV_Name 2" to create the mirror on a LV.
"syncvg –l LV_Name" to start synchronizing the mirror.
When the mirror is synchronized:
"unmirrorvg VG_vgname hdisk_to_remove_from_mirror" to break mirroring
And "rmdev –l hdisk_name –d" to remove the old disk from the mirror.
Thanks,
Dominique

 

[khalidaaa]

It seems perfect to me

Regards,
Khalid

 

[zaxxon]

Sounds good - maybe you should import the VG that contains the new LV is on on the other node(s) in your cluster so that they will accept the changed VG, when a takeover is occuring.

If possible, take a downtime outside production time and run a forced takeover to check if, the other node(s) accept the changed VG, just to be sure.

Maybe your HACMP environment uses an "importvg -L" to learn about changes on the VG.
There could also be the case you might have to use a "chvg -g" to make them accept it.

Whatever - if your application is so critical that it is place on a HACMP cluster, make sure it works when a takeover occurs.

laters
zaxxon

 

[domi1805]

Hello,
Thank you, but for the mirroring, I don't use a new VG but I will add the new disks to the existing VG in order to be able to do the mirroring.

And it seems that a disk can be used for the heartbeat. Is there any impact with mirroring, as mirroring works with normal LV containing the data but the heartbeat is probably a special location on disk that cannot be mirrored with LVM.

Dominique

 

[zaxxon]

I didn't write you had a new VG but a changed VG with maybe a new LV or at least a new size for a LV/FS which should be made known to the other node(s), which will varyon that VG, when a takeover happens.

laters
zaxxon

 

[domi1805]

ok, you are right. Thank you.
But what about this heartbeat on disk? Is it possible to migrate it on another hdisk using LVM mirroring also?
Dominique

 

[zaxxon]

Yes you can use a disk for heartbeat, since HACMP 5.1 and must be shared, so that every node in the cluster can reach it. It can also be a production disk that has already data on it.
I would take an extra small LUN/disk on SAN without working data (just my personal taste) or directly attached to all nodes; that on a RAID1 should be sufficient.

More information is here:

http://www.redbooks.ibm.com/abstracts/sg246375.html?Open

http://www.redbooks.ibm.com/abstracts/sg246769.html?Open

laters
zaxxon