Intel Modular Server: KVM guest access to shared LUN

[drd]

Hi,

I'm considering to use the Intel Modular Server (with dual SAS controller and dual Ethernet cards) to run a Proxmox cluster on three compute modules. The hardware has not been purchased yet.

I want to use shared LVM storage for KVM guests, using the shared LUN software option. I expect no issues here.

One of the things I want to run on the Proxmox cluster is a KVM guest that acts as CIFS/NFS file server. Running this as a VM instead of directly on the IMS hardware has the advantage of better resource utilization and live migration to another compute module. However, I don't like to put my files in the regular virtual machine's disk. I want them to reside on a virtual disk on the IMS, which the KVM guest would directly access (e.g. putting something like "ide2: /dev/sdb" in the VM config). The "difficulty" here is that this virtual disk still needs to be accessible after a (live) migration. I could remap the virtual drive on the IMS to another compute module, but instead I thought I'd use the shared LUN feature again to make this disk available to all compute modules upfront. Only the one actually running the VM would access it.

Can this work, or have I overlooked something?

Many thanks,
David

 

[tom]

Follow this guide: http://pve.proxmox.com/wiki/Intel_Modular_Server
I see no problems here.

just to mention, we did not test MPIO configuration (dual SAS) here as we have no second SAS controller in the test lab.

 

[drd]

Okay, thanks for your reply.

Dual SAS is indeed something that may cause trouble. I hope to get a demo chassis from our supplier with dual SAS to be able to try it out before purchasing.

 

[tom]

yes, that´s what I would recommend. another strategy is just going for two boxes (with single SAS). If you have enough space in your rack its a quite good setup as you have a full second box in case of issues, you can also use it for spare parts.

 

[drd]

I want them to reside on a virtual disk on the IMS, which the KVM guest would directly access (e.g. putting something like "ide2: /dev/sdb" in the VM config). The "difficulty" here is that this virtual disk still needs to be accessible after a (live) migration.

This doesn't work I'm afraid.

In my VM config, I added:

ide1: /dev/mapper/shareddata-data

This is a LVM logical volume "data" inside the volume group "shareddata", created on the cluster master. VM 102 is running on the master, and I want it to migrate to the other node. Thanks to the shared LUN feature, this VG and LV is perfectly visible on the other node. The IP address below is that of the other node:

/usr/sbin/qmigrate 10.4.8.172 102
Apr 27 15:16:10 starting migration of VM 102 to host '10.4.8.172'
Apr 27 15:16:10 copying disk images
Apr 27 15:16:10 Failed to sync data - cant migrate local file/device '/dev/mapper/shareddata-data'
Apr 27 15:16:10 migration aborted
VM 102 migration failed -

Any suggestion as to how I can "force" the migration, since I know the "local file/device" is already present at the destination?

Thanks,
David