It's the standard clustering problem. Any software that does any sort of avtive clustering is going to fence nodes that have problems, or should if it cares about your data. If the risk of losing a host due to a storage pool outage is too great, you could perhaps look at rearranging your pool-to-host correlations (certain hosts run vms from certain pools) via clusters. Note that if you register a storage pool with a cluster, it will register the pool with libvirt when the pool is not in maintenance, which, when the storage pool goes down will cause problems for the host even if no VMs from that storage are running (fetching storage stats for example will cause agent threads to hang if its NFS), so you'd need to put ceph in its own cluster and NFS in its own cluster.
It's far more dangerous to leave a host in an unknown/bad state. If a host loses contact with one of your storage nodes, with HA, cloudstack will want to start the affected VMs elsewhere. If it does so, and your original host wakes up from it's NFS hang, you suddenly have a VM running in two locations, corruption ensues. You might think we could just stop the affected VMs, but NFS tends to make things that touch it go into D state, even with 'intr' and other parameters, which affects libvirt and the agent. We could perhaps open a feature request to disable all HA and just leave things as-is, disallowing operations when there are outages. If that sounds useful you can create the feature request on https://issues.apache.org/jira. On Mon, Mar 3, 2014 at 5:37 AM, Andrei Mikhailovsky <and...@arhont.com> wrote: > > Koushik, I understand that and I will put the storage into the maintenance > mode next time. However, things happen and servers crash from time to time, > which is not the reason to reboot all host servers, even those which do not > have any running vms with volumes on the nfs storage. The bloody agent just > rebooted every single host server regardless if they were running vms with > volumes on the rebooted nfs server. 95% of my vms are running from ceph and > those should have never been effected in the first place. > ----- Original Message ----- > > From: "Koushik Das" <koushik....@citrix.com> > To: "<us...@cloudstack.apache.org>" <us...@cloudstack.apache.org> > Cc: dev@cloudstack.apache.org > Sent: Monday, 3 March, 2014 5:55:34 AM > Subject: Re: ALARM - ACS reboots host servers!!! > > The primary storage needs to be put in maintenance before doing any > upgrade/reboot as mentioned in the previous mails. > > -Koushik > > On 03-Mar-2014, at 6:07 AM, Marcus <shadow...@gmail.com> wrote: > >> Also, please note that in the bug you referenced it doesn't have a >> problem with the reboot being triggered, but with the fact that reboot >> never completes due to hanging NFS mount (which is why the reboot >> occurs, inaccessible primary storage). >> >> On Sun, Mar 2, 2014 at 5:26 PM, Marcus <shadow...@gmail.com> wrote: >>> Or do you mean you have multiple primary storages and this one was not >>> in use and put into maintenance? >>> >>> On Sun, Mar 2, 2014 at 5:25 PM, Marcus <shadow...@gmail.com> wrote: >>>> I'm not sure I understand. How do you expect to reboot your primary >>>> storage while vms are running? It sounds like the host is being >>>> fenced since it cannot contact the resources it depends on. >>>> >>>> On Sun, Mar 2, 2014 at 3:24 PM, Nux! <n...@li.nux.ro> wrote: >>>>> On 02.03.2014 21:17, Andrei Mikhailovsky wrote: >>>>>> >>>>>> Hello guys, >>>>>> >>>>>> >>>>>> I've recently came across the bug CLOUDSTACK-5429 which has rebooted >>>>>> all of my host servers without properly shutting down the guest vms. >>>>>> I've simply upgraded and rebooted one of the nfs primary storage >>>>>> servers and a few minutes later, to my horror, i've found out that all >>>>>> of my host servers have been rebooted. Is it just me thinking so, or >>>>>> is this bug should be fixed ASAP and should be a blocker for any new >>>>>> ACS release. I mean not only does it cause downtime, but also possible >>>>>> data loss and server corruption. >>>>> >>>>> >>>>> Hi Andrei, >>>>> >>>>> Do you have HA enabled and did you put that primary storage in maintenance >>>>> mode before rebooting it? >>>>> It's my understanding that ACS relies on the shared storage to perform HA >>>>> so >>>>> if the storage goes it's expected to go berserk. I've noticed similar >>>>> behaviour in Xenserver pools without ACS. >>>>> I'd imagine a "cure" for this would be to use network distributed >>>>> "filesystems" like GlusterFS or CEPH. >>>>> >>>>> Lucian >>>>> >>>>> -- >>>>> Sent from the Delta quadrant using Borg technology! >>>>> >>>>> Nux! >>>>> www.nux.ro > >
