<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Jan 30, 2017 at 6:25 AM, Niklaus Hofer <span dir="ltr"><<a href="mailto:niklaus.hofer@stepping-stone.ch" target="_blank">niklaus.hofer@stepping-stone.ch</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi<br>
<br>
I have a question concerning the 'correct' behaviour of GlusterFS:<br>
<br>
We a nice Gluster setup up and running. Most things are working nicely. Our setup is as follows:<br>
- Storage is a 2+1 Gluster setup (2 replicating hosts + 1 arbiter) with a volume for virtual machines.<br>
- Two virtualisation hosts running libvirt / qemu / kvm.<br>
<br></blockquote><div><br></div><div>Are you using something like oVirt or proxmox for managing your virtualization cluster?</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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)?<br>
Initially we were hoping that the virtualisation hosts would automatically switch over to the second storage node and keep all VMs running.<br>
<br>
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.<br>
<br>
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:<br>
- If the virtualisation host is connected to the storage node which is still running:<br>
- everything is fine and the VM keeps running<br>
- If the virtualisation host was connected to the storage node which is now absent:<br>
- qemu is supposed to 'pause' / 'freeze' the VM<br>
- Virtualisation host waits for ping timeout<br>
- Virtualisation host switches over to the other storage node<br>
- qemu 'unpauses' the VMs<br>
- The VM is fully operational again<br>
<br>
Does my description match the 'optimal' GlusterFS behaviour?<br></blockquote><div><br></div><div><br></div><div>Can you provide more details about your gluster volume configuration and the options enabled on the volume?</div><div><br></div><div>Regards,</div><div>Vijay </div></div></div></div>