[CentOS-virt] Basic shared storage + KVM

Tue Jun 19 16:21:46 UTC 2012
Andrea Chierici <andrea.chierici at cnaf.infn.it>

I am trying to set up a shared iscsi storage to serve 6 kvm hypervisors 
running centos 6.2.
I export an LVM from iscsi and configured virt-manager to see the iscsi 
space as LVM storage (a single storage pool).
I can create space on this LVM storage pool directly from virt-manager 
and I am already running a couple of sample VMs, that do migrate from 
one hv to the other.

This configuration has a problem: when I create a new LV on the LVM 
storage pool to host a new VM, the HV where I am creating the virtual 
machine on sees the LV as status "available", while the others see it as 
"NOT available". In some circumstances this can crash libvirtd. To fix 
this I generally issue:

vgchange -an; sleep 1; vgchange -ay

but sometimes this fails with error:

device-mapper; create ioctl failed: Device or resource busy

and anyway it's not very convenient to issue this command on every node 
every time a new LV is created.
Can anyone suggest a solution (if any) to this problem?
Keep in mind that the basic concept behind this approach is to keep 
things as simple as possible. I don't want to configure a cluster or any 
other complicated tool to simply be able to migrate VMs from one HV to 


Andrea Chierici - INFN-CNAF 			
Viale Berti Pichat 6/2, 40127 BOLOGNA
Office Tel: +39 051 6092809	
ICQ#2328798, MSN#ataruz<at>gmail.com, Skype#ataruz