On Mon, Jan 30, 2017 at 6:25 AM, Niklaus Hofer < [email protected]> wrote:
> Hi > > I have a question concerning the 'correct' behaviour of GlusterFS: > > We a nice Gluster setup up and running. Most things are working nicely. > Our setup is as follows: > - Storage is a 2+1 Gluster setup (2 replicating hosts + 1 arbiter) with a > volume for virtual machines. > - Two virtualisation hosts running libvirt / qemu / kvm. > > Are you using something like oVirt or proxmox for managing your virtualization cluster? > Now the question is, what is supposed to happen when we unplug one of the > storage nodes (aka power outage in one of our data centers)? > Initially we were hoping that the virtualisation hosts would automatically > switch over to the second storage node and keep all VMs running. > > However, during our tests, we have found that this is not the case. > Instead, when we unplug one of the storage nodes, the virtual machines run > into all sorts of problems; being unable to read/write, crashing > applications and even corrupting the filesystem. That is of course not > acceptable. > > Reading the documentation again, we now think that we have misunderstood > what we're supposed to be doing. To our understanding, what should happen > is this: > - If the virtualisation host is connected to the storage node which is > still running: > - everything is fine and the VM keeps running > - If the virtualisation host was connected to the storage node which is > now absent: > - qemu is supposed to 'pause' / 'freeze' the VM > - Virtualisation host waits for ping timeout > - Virtualisation host switches over to the other storage node > - qemu 'unpauses' the VMs > - The VM is fully operational again > > Does my description match the 'optimal' GlusterFS behaviour? > Can you provide more details about your gluster volume configuration and the options enabled on the volume? Regards, Vijay
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