I use KVM on two identical centos5 hosts.
I can live migrate the virtual machines from one to the other and it works great. Once I do this, I can see VM definitions on both hosts using virt-manager or virsh list --all On one machine the VM is running, on the other it reports "shut off". The disk images are accessible to both host machines and I want to have only one running a the time (of course). If the VM locks up, I could by mistake think that the machine is not running and try to start it on the wrong host.
My question is, how can I prevent host A from starting a "shut off" VM that actually has been migrated to host B? The VM could actually be running on any another host. It could also have been crashed. The most simple solution would be some sort of lock file placed next to the disk image location, so seen by all hosts. But perhaps there is another way of working with virt-manager that I am not aware of?
Theo
-----Original Message----- From: centos-bounces@centos.org [mailto:centos-bounces@centos.org] On Behalf Of Theo Band Sent: 11 May 2012 11:51 To: CentOS mailing list Subject: [CentOS] How to prevent virtual machines running twice on the disk images?
I use KVM on two identical centos5 hosts.
I can live migrate the virtual machines from one to the other and it works great. Once I do this, I can see VM definitions on both hosts using virt- manager or virsh list --all On one machine the VM is running, on the other it reports "shut off". The disk images are accessible to both host machines and I want to have only one running a the time (of course). If the VM locks up, I could by mistake think that the machine is not running and try to start it on the wrong host.
My question is, how can I prevent host A from starting a "shut off" VM that actually has been migrated to host B? The VM could actually be running on any another host. It could also have been crashed. The most simple solution would be some sort of lock file placed next to the disk image location, so seen by all hosts. But perhaps there is another way of working with virt- manager that I am not aware of?
Theo
Are those machines clustered? I used drbd/pacemaker/corosync to achieve something similar across two CentOS hosts with KVM machines, and the VM can only be started on the master node where the DRBD drive is mounted and accessible. Live migrations are fairly easy too with this method
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On 05/11/2012 01:07 PM, Regendoerp, Achim wrote:
-----Original Message----- From: centos-bounces@centos.org [mailto:centos-bounces@centos.org] On Behalf Of Theo Band Sent: 11 May 2012 11:51 To: CentOS mailing list Subject: [CentOS] How to prevent virtual machines running twice on the disk images?
I use KVM on two identical centos5 hosts.
I can live migrate the virtual machines from one to the other and it works great. Once I do this, I can see VM definitions on both hosts using virt- manager or virsh list --all On one machine the VM is running, on the other it reports "shut off". The disk images are accessible to both host machines and I want to have only one running a the time (of course). If the VM locks up, I could by mistake think that the machine is not running and try to start it on the wrong host.
My question is, how can I prevent host A from starting a "shut off" VM that actually has been migrated to host B? The VM could actually be running on any another host. It could also have been crashed. The most simple solution would be some sort of lock file placed next to the disk image location, so seen by all hosts. But perhaps there is another way of working with virt- manager that I am not aware of?
Theo
Are those machines clustered? I used drbd/pacemaker/corosync to achieve something similar across two CentOS hosts with KVM machines, and the VM can only be started on the master node where the DRBD drive is mounted and accessible. Live migrations are fairly easy too with this method
No, not clustered. drbd I do use, but that means a drbd block devices for every individual vm. I tried that but find it a lot of effort to maintain. One shared (NFS) filesystem gives a lot more freedom to move a VM to a machine host machine that has a lower load. I don't mind doing that by hand. It's not for high availability.
Theo
-----Original Message----- From: centos-bounces@centos.org [mailto:centos-bounces@centos.org] On Behalf Of Theo Band Sent: 11 May 2012 12:28 To: CentOS mailing list Subject: Re: [CentOS] How to prevent virtual machines running twice on the disk images?
On 05/11/2012 01:07 PM, Regendoerp, Achim wrote:
-----Original Message----- From: centos-bounces@centos.org [mailto:centos-bounces@centos.org]
On
Behalf Of Theo Band Sent: 11 May 2012 11:51 To: CentOS mailing list Subject: [CentOS] How to prevent virtual machines running twice on the disk images?
I use KVM on two identical centos5 hosts.
I can live migrate the virtual machines from one to the other and it works great. Once I do this, I can see VM definitions on both hosts using virt- manager or virsh list --all On one machine the VM is running, on the other it reports "shut off". The disk images are accessible to both host machines and I want to have only one running a the time (of course). If the VM locks up, I could by mistake think that the machine is not running and try to start it
on the wrong host.
My question is, how can I prevent host A from starting a "shut off" VM that actually has been migrated to host B? The VM could actually be running on any another host. It could also have been crashed. The most simple solution would be some sort of lock file placed next to the disk image location, so seen by all hosts. But perhaps there is another way of working with virt- manager that I am not aware of?
Theo
Are those machines clustered? I used drbd/pacemaker/corosync to achieve something similar across two CentOS hosts with KVM machines, and the VM can only be started on the master node where the DRBD drive is mounted and accessible. Live migrations are fairly easy too with this method
No, not clustered. drbd I do use, but that means a drbd block devices for every individual vm. I tried that but find it a lot of effort to maintain. One shared (NFS) filesystem gives a lot more freedom to move a VM to a machine host machine that has a lower load. I don't mind doing that by hand. It's not for high availability.
Theo
Hm, I've used one block device for multiple VMs, which made it easier, and prevent the hassle with x block devices for x VMs. Other than that, no idea if virt-manager can do what you're looking for.
Achim
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Emails are not secure and cannot be guaranteed to be error-free, as they can be intercepted, amended, lost or destroyed, and may contain viruses; anyone who communicates with us by email is taken to accept these risks. GCG accepts no liability for any loss or damage which may be caused by software viruses.
On Fri, 2012-05-11 at 12:51 +0200, Theo Band wrote:
I use KVM on two identical centos5 hosts.
I can live migrate the virtual machines from one to the other and it works great. Once I do this, I can see VM definitions on both hosts using virt-manager or virsh list --all On one machine the VM is running, on the other it reports "shut off". The disk images are accessible to both host machines and I want to have only one running a the time (of course). If the VM locks up, I could by mistake think that the machine is not running and try to start it on the wrong host.
My question is, how can I prevent host A from starting a "shut off" VM that actually has been migrated to host B? The VM could actually be running on any another host. It could also have been crashed. The most simple solution would be some sort of lock file placed next to the disk image location, so seen by all hosts. But perhaps there is another way of working with virt-manager that I am not aware of?
Theo
This may not be what you are looking for, but you could always dump the xml of the domain to a file (so you could define/start it again if needed), then undefine the domain using virsh.
On Fri, 11 May 2012, Theo Band wrote:
I use KVM on two identical centos5 hosts. [....]
My question is, how can I prevent host A from starting a "shut off" VM that actually has been migrated to host B? The VM could actually be running on any another host. It could also have been crashed. The most simple solution would be some sort of lock file placed next to the disk image location, so seen by all hosts. But perhaps there is another way of working with virt-manager that I am not aware of?
My way of dealing with that is to undefine the domain on host A after it's been moved to host B, e.g.,
virsh migrate --live myvm remote://host-b virsh undefine myvm
The CentOS 6 version of virsh allows those operations to be combined:
virsh migrate --live --persistent --undefinesource myvm ...
On 05/11/2012 06:06 PM, Paul Heinlein wrote:
On Fri, 11 May 2012, Theo Band wrote:
I use KVM on two identical centos5 hosts. [....]
My question is, how can I prevent host A from starting a "shut off" VM that actually has been migrated to host B? The VM could actually be running on any another host. It could also have been crashed. The most simple solution would be some sort of lock file placed next to the disk image location, so seen by all hosts. But perhaps there is another way of working with virt-manager that I am not aware of?
My way of dealing with that is to undefine the domain on host A after it's been moved to host B, e.g.,
virsh migrate --live myvm remote://host-b virsh undefine myvm
The CentOS 6 version of virsh allows those operations to be combined:
virsh migrate --live --persistent --undefinesource myvm ...
Thanks, that's the tip I needed. "undefine".
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Paul Heinlein -
Regendoerp, Achim -
Tait Clarridge -
Theo Band