Online migration solution between tro DRBD storages ?

[plewka]

We would like to use _two_ DRBD devices for the "show"
als recommened in older documents on this page.

Usually one is primary on one node and secondary on the other
and vice versa.
primary/secondary
secodary/primary

If one machine needs service we would have to switch to:
primary/primary
primary/primary

and later to:
primary/secondary
primary/secondary

But if something gets wrong while running primary/primary
and it comes to splitbrain you understand it would be very
helpfull to online migrate from one storage to the other
and prevent primary/primary.

Any ideas how to do it using LVM?
I remember PVE1.x did something like that in the earlier
days, didn't it? How?

Thanks in advance!

 

[e100]

I have many nodes using DRBD and always run in primary/primary and split brain is of no concern to me, very simple to recover from and usually very quick too.

Make sure you have two DRBD volumes, VMs running on node A are placed onto DRBD0 and VMs on node B are placed onto DRBD1.
The only time a split brain can be an issue is if you are migrating all the node A VMs to node B and it split brains before you have moved all of them.


There currently is no way to migrate to a different storage.
There was some promising looking code in KVM to make this possible(live block migration), I even tested it and it worked.
Issue is the KVM devs removed it (apparently it was unstable) and they mentioned they plan to implement a similar feature in a better more stable way.
Hopefully the KVM devs will implement something reliable in the not too distant future and then Proxmox will add support for it.

This old thread mentions that the feature in 1.X you are thinking of was removed:
http://forum.proxmox.com/threads/4609-live-migration-with-non-shared-storage

I remember testing it a few times, it was super slow.