[PVE-User] Access disk space from multiple VMs. Is that possible?

Gilles Mocellin gilles.mocellin at nuagelibre.org
Tue Jan 24 20:30:46 CET 2012

Le 24/01/2012 12:58, Tom H. Lautenbacher a écrit :
> Hello Proxmox users,


> is it possible to have disk space on a Proxmox server that is accessible
> from multiple VMs?
> Here is an example of what I want to do:
> 1 Server, having a 8-disk-RAID6 on a 3ware 9650SE-8LPML controller. On
> this RAID volume lives Proxmox and:
> - "Diskspace A" with some terrabyte of diskspace
> - VM1: Samba Fileserver (not holding any own data but serving the data
> on "Diskspace A")
> - VM2: FTP Server (not holding any own data but serving the data on
> "Diskspace A")
> - VM3: HTTP Server (not holding any own data but serving the data on
> "Diskspace A")
> All three VMs should have full read/write access to "Diskspace A" and be
> able to access "Diskspace A" simultaneously without interfering each other.
> - Is this possible?

Every thing is possible, but not always easily or supported...
2 ways :
- NFS from host to VMs
- share a logical volume between VMs

> - Are there any limitations?

Of course.
- For NFS :
   - proxmox host must be NFS server ready
- For LVM :
   - block device sharing, you must use a clustered filesystem to handle 
concurrent mounts (GFS, OCFS).
   - Proxmox Web Interface does not permit to use the same drive in two 
VMs, the block device (logical volume) is named with the VM ID... But, 
you can edit manually the VM conf to use the same drive of another VM.

> - is this a good thing to do

I don't thing so, why not just share via SMB, FTP and HTTP on the same VM ?

> - how would I do it?

- Fot NFS from host to VM, it can be straight forward, excpet if the 
proxmox kernel does not support kernel NFS server.
- For shared block device, you must :
   - use KVM for virtualisation
   - edit the VM configuration file (/etc/qemu-server/XYZ.conf) to add a 
virtio drive based on the same logical volume for the 3 VMs
   - int the VMs use a clustered filesystem with the associated 
clusterware (GFS ith RedHat CLusterSuite / cman, OCFS with its own 
cluster ware or heartbeat or pacemaker)

=> As you see, it's not really easy...

> I am glad for any peace of information, help, hints, etc..
> Thank you
> Tom
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