[ovirt-users] Engine migration and host import
Ben Bradley
listsbb at virtx.net
Mon Sep 25 23:29:59 UTC 2017
On 25/09/17 13:56, Simone Tiraboschi wrote:
>
>
> On Sun, Sep 24, 2017 at 10:59 PM, Ben Bradley <listsbb at virtx.net
> <mailto:listsbb at virtx.net>> wrote:
>
> On 23/09/17 00:27, Ben Bradley wrote:
>
> On 20/09/17 15:41, Simone Tiraboschi wrote:
>
>
> On Wed, Sep 20, 2017 at 12:30 AM, Ben Bradley
> <listsbb at virtx.net <mailto:listsbb at virtx.net>
> <mailto:listsbb at virtx.net <mailto:listsbb at virtx.net>>> wrote:
>
> Hi All
>
> I've been running a single-host ovirt setup for several
> months,
> having previously used a basic QEMU/KVM for a few years
> in lab
> environments.
>
> I currently have the ovirt engine running at the
> bare-metal level,
> with the box also acting as the single host. I am also
> running this
> with local storage.
>
> I now have an extra host I can use and would like to
> migrate to a
> hosted engine. The following documentation appears to
> be perfect and
> pretty clear about the steps involved:
> https://www.ovirt.org/develop/developer-guide/engine/migrate-to-hosted-engine/
> <https://www.ovirt.org/develop/developer-guide/engine/migrate-to-hosted-engine/>
>
>
> <https://www.ovirt.org/develop/developer-guide/engine/migrate-to-hosted-engine/
> <https://www.ovirt.org/develop/developer-guide/engine/migrate-to-hosted-engine/>>
>
> and
> https://www.ovirt.org/documentation/self-hosted/chap-Migrating_from_Bare_Metal_to_an_EL-Based_Self-Hosted_Environment
> <https://www.ovirt.org/documentation/self-hosted/chap-Migrating_from_Bare_Metal_to_an_EL-Based_Self-Hosted_Environment>
>
>
> <https://www.ovirt.org/documentation/self-hosted/chap-Migrating_from_Bare_Metal_to_an_EL-Based_Self-Hosted_Environment
> <https://www.ovirt.org/documentation/self-hosted/chap-Migrating_from_Bare_Metal_to_an_EL-Based_Self-Hosted_Environment>>
>
>
> However I'd like to try and get a bit more of an
> understanding of
> the process that happens behind the scenes during the
> cut-over from
> one engine to a new/hosted engine.
>
> As an experiment I attempted the following:
> - created a new VM within my current environment
> (bare-metal engine)
> - creating an engine-backup
> - stopped the bare-metal engine
> - restored the backup into the new VM
> - ran engine-setup within the new VM
> The new engine started up ok and I was able to connect
> and login to
> the web UI. However my host was "unresponsive" and I
> was unable to
> manage it in any way from the VM. I shut the VM down
> and started the
> bare-metal ovirt-engine again on the host and
> everything worked as
> before. I didn't try very hard to make it work however.
>
> The magic missing from the basic process I tried is the
> synchronising and importing of the existing host, which
> is what the
> hosted-engine utility does.
>
>
> No magic up to now: the host are simply in the DB you restored.
> If the VM has network connectivity and the same host-name of
> the old machine you shouldn't see any issue.
> If you changed the host-name moving to the VM, you should
> simply run engine-rename after the restore.
>
>
> Thank you for the reply.
> I tried this again this evening - again it failed.
>
> The host is present within the new engine but I am unable to
> manage it.
> Host is marked as down but Activate is greyed out. I can get get
> into the "Edit" screen for the host and on right-click I get the
> following options:
> - Maintenance
> - Confirm Host has been Rebooted
> - SSH Management: Restart and Stop both available
> The VMs are still running and accessible but are not listed as
> running under the web interface. This time however I did lose
> access to the ovirtmgmt bridge and the web interface, running
> VMs and host SSH session were unavailable until I rebooted.
> Luckily I left ovirt-engine service enabled to restart on boot
> so everything came back up.
>
> The engine URL is a CNAME so I just re-pointed to the hostname
> of the VM just before running engine-setup after the restore.
>
> This time though I have kept the new engine VM so I can power it
> up again and try and debug.
>
> I am going to try a few times over the weekend and I have setup
> serial console access so I can do a bit more debugging.
>
> What ovirt logs could I check on the host to see if the new
> engine VM is able to connect and sync to the host properly?
>
> Thanks, Ben
>
>
> So I tried again to migrate my bare-metal host to a hosted VM but no
> luck. The host remained in unresponsive state in the engine web UI
> and I was unable to manage the host in anyway. Although all VMs
> continued to run.
>
> I did capture some logs though.
> From the new engine VM... engine.log
> https://p.bsd-unix.net/view/raw/666839d1
> <https://p.bsd-unix.net/view/raw/666839d1>
>
> From the host...
> mom.log https://p.bsd-unix.net/view/raw/ac9379f0
> <https://p.bsd-unix.net/view/raw/ac9379f0>
> supervdsm.log https://p.bsd-unix.net/view/raw/f9018dec
> <https://p.bsd-unix.net/view/raw/f9018dec>
> vdsm.log https://p.bsd-unix.net/view/raw/bcdcdb13
> <https://p.bsd-unix.net/view/raw/bcdcdb13>
>
>
> Sorry but no one of that links is working right now.
>
> The engine VM is complaining about being unable to connect to the
> host, though I can see from tcpdump communication is fine. I believe
> this is backed up by the pings seen in mom.log
>
> Though I can see the following in vdsm.log... [vds] recovery:
> waiting for storage pool to go up (clientIF:569)
> So I wonder if this is blocking the engine bringing the host up.
>
> The host is running local storage, which I believe is a pretty
> recent addition to ovirt. So I could see how trying to run an engine
> VM on a host's local storage might cause weird issues.
>
>
> Maybe I lost a piece here.
> Are you trying to migrate an old 3.6 all-in-one setup (where
> ovirt-engine - the manager - and vdsm - the agent on the host are
> running on the same host) to hosted-engine in a single step?
> In that case it will not work for sure since when you will power-down
> the old engine machine you will also power-down your old host and so the
> new engine running on the VM is not able to contact the host since the
> old host is down.
>
> In hosted-engine idea, the engine runs on a VM running on the host that
> its managing.
>
> In that case probably the most effective way is to:
> within your old engine:
> - create a datacenter with shared storage (please avoid using NFS in
> loopback)
> - add your new hosts there
> - migrate all of your VMs to the new dataceter
> - only now you can migrate to hosted-engine
Thank you for the further reply. Those links appear to work for me now
so perhaps it was a temporary failure.
At the moment I am running engine 4.1.4.2-1.el7 on CentOS 7.3.1611
It's on a bare-metal machine, the same machine is acting as the host,
and all accessing local storage (ISO domain and a VM datastore).
So it's an all-in-one setup but of my own installation, not using any
previous all-in-one installation scripts.
I basically installed ovirt engine on a machine, then deployed the host
onto the same machine, then setup local datastores.
Is this a possible (though not necessarily supported) migration path in
any way?
It sounds like shared storage is basically a prerequisite for hosted
engine after all - not running it off a single host's local storage.
Thanks
> I realise that there won't be HA with this setup, until I create my
> second host and configure HA on the VM.
>
> If I am unable to migrate from bare-metal -> engine VM then it
> doesn't give me any confidence that I would be able to restore a
> setup from a backup onto a bare-metal host and recover host state.
>
> So is the only supported method of migrating from bare-metal engine
> to hosted engine by...
> 1) Migrating to the appliance
> 2) Using a new host to migrate to VM
> 3) Using shared storage between hosts
>
> Thanks, Ben
>
>
>
> The only detail is that hosted-engine-setup will try to add
> the host where you are running it to the engine and so you
> have to manually remove it just after the restore in order
> to avoid a failure there.
>
>
> Can anyone describe that process in a bit more detail?
> Is it possible to perform any part of that process
> manually?
>
> I'm planning to expand my lab and dev environments so
> for me it's
> important to discover the following...
> - That I'm able to reverse the process back to
> bare-metal engine if
> I ever need/want to
> - That I can setup a new VM or host with nothing more
> than an
> engine-backup but still be able to regain control of
> exiting hosts
> and VMs within the cluster
>
> My main concern after my basic attempt at a
> "restore/migration"
> above is that I might not be able to re-import/sync an
> existing host
> after I have restored engine from a backup.
>
> I have been able to export VMs to storage, remove them
> from ovirt,
> re-install engine and restore, then import VMs from the
> export
> domain. That all worked fine. But it involved shutting
> down all VMs
> and removing their definitions from the environment.
>
> Are there any pre-requisites to being able to re-import
> an existing
> running host (and VMs), such as placing ALL hosts into
> maintenance
> mode and shutting down any VMs first?
>
> Any insight into host recovery/import/sync processes
> and steps will
> be greatly appreciated.
>
> Best regards
> Ben
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