On Mon, Feb 6, 2017 at 1:52 PM, Doug Ingham <dou...@gmail.com> wrote:
> Hi All, Simone, > > On 24 January 2017 at 10:11, Simone Tiraboschi <stira...@redhat.com> > wrote: > >> >> >> On Tue, Jan 24, 2017 at 1:49 PM, Doug Ingham <dou...@gmail.com> wrote: >> >>> Hey guys, >>> Just giving this a bump in the hope that someone might be able to >>> advise... >>> >>> Hi all, >>>> One of our engines has had a DB failure* & it seems there was an >>>> unnoticed problem in its backup routine, meaning the last backup I've got >>>> is a couple of weeks old. >>>> Luckily, VDSM has kept the underlying VMs running without any >>>> interruptions, so my objective is to get the HE back online & get the hosts >>>> & VMs back under its control with minimal downtime. >>>> >>>> So, my questions are the following... >>>> >>>> 1. What problems can I expect to have with VMs added/modified since >>>> the last backup? >>>> >>>> Modified VMs will be reverted to the previous configuration; additional >> VMs should be seen as external VMs, then you could import. >> > > Given VDSM kept the VMs up whilst the HE's been down, how will the running > VMs that were present before & after the backup be affected? > > Many of the VMs that were present during the last backup are now on > different hosts, including the HE VM. Will that cause any issues? > For normal VMs I don't expect any issue: the engine will simply update the correspondent record once it will find them on the managed hosts. A serious issue could instead happen with HA VMs: if the engine finds earlier an HA VM as running on a different host it will simply update its record, the issue is if it finds earlier the VM a not on the original host since it will try to restart it causing a split brain and probably a VM corruption. I opened a bug to track it: https://bugzilla.redhat.com/show_bug.cgi?id=1419649 > > >> >> >>> >>>> 1. As it's only the DB that's been affected, can I skip redeploying >>>> the Engine & jump straight to restoring the DB & rerunning engine-setup? >>>> >>>> >> Yes, if the engine VM is fine, you could just import the previous backup >> and run engine-setup again. >> Please set the global maintenance mode for hosted-engine since >> engine-backup and engine-setup are going to bring down the engine. >> > > As per above, do I still only need to import the previous backup even if > the all of the VMs (including the HE VM) are now on different hosts to when > the backup was made? > Please take care of the HA VMs. > > > And as for the future, is it going to be necessary to always keep an > unused host in the cluster to allow for emergency restores? I'm a bit > concerned that if we ever utilised all of our hosts for running VMs, then > we'd be completely stuck if the HE ever imploded again. > Honestly I don't see any special issue there. > > Cheers, > -- > Doug >
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