[PVE-User] shared LVM on host-based mirrored iSCSI LUNs

Flavio Stanchina flavio.stanchina at ies.it
Mon Apr 23 18:10:51 CEST 2012

Stefan Sänger wrote:
> Let me first describe the setup:
> I have two small NAS boxes running openfiler each providing an iSCSI
> LUN. These LUNs are exactly the same size.
> I connected both LUNs to all three of my proxmox-servers (pve1, pve2 and
> pve2).
> In order to implement host-based mirroring I installed mdadm on each
> proxmox server and created a RAID1 on pve1 using both LUNs. (/dev/md0)
> Then I created a physical volume on that RAID and a new volume group
> (/dev/vgiscsi).
> After restarting mdadm and excuting pvscan the volume group was visible
> on all 3 servers.

Not safe, as far as I know. It would be just like using a 
non-distributed filesystem such as extX on shared storage: md is not 
meant to be used in this way, there is no locking between multiple 
nodes. While I can't think of a sure way to break it, I wouldn't feel 
safe to use it in production.

Use DRBD between the two NAS boxes -- or whatever kind of realtime 
mirroring OpenFiler has to offer -- to mirror the disks, then use 
multipath to expose both ends to the VM hosts.

Flavio Stanchina
Informatica e Servizi
Trento - Italy

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