[ovirt-users] upgrade hosted-engine os ( not hosts )

[Simone Tiraboschi]

On Thu, Jun 30, 2016 at 8:34 AM, Paul Groeneweg | Pazion <paul at pazion.nl> wrote:
> Hi Yedidyah,
>
> Thank you for the comprehensive answers.
>
> I think I go for a complete reinstall ( read also OS upgrade tool is not
> adviced on 6.6 or higher as there might be newer packages as on 7 ). No
> doubting to re-use current VM or setup from scratch ( fresh host with new
> hosted-engine and existing storage domein ).

If you are planning to redeploy hosted-engien from scratch and
restoring on the new engine DB a backup of the previous one, please
carefully consider this:
https://bugzilla.redhat.com/show_bug.cgi?id=1240466#c21

So, if you choose that path you'll have also to manually remove any
reference to the previous hosted-engine from the restored DB.
I'd strongly suggest you to wait for the upgrade tool to be fixed
since manually doing this upgrade can be really error prone.

> You explain the steps ( 1 to 6 ), but then don't talk about storage domain
> import.
> Does it mean, when I reinstall the hosted-engine in the current he VM and
> restore an engine-backup ( step 5 ) I am able to start vm from Host and it
> is still connected to the master storage ( so no need for storage import) ?
>
> Best Regards,
> Paul Groeneweg
>
>
> Op do 30 jun. 2016 om 08:00 schreef Yedidyah Bar David <didi at redhat.com>:
>>
>> On Wed, Jun 29, 2016 at 10:07 PM, Paul Groeneweg | Pazion
>> <paul at pazion.nl> wrote:
>> >
>> > I am looking for a way to get my hosted-engine running on el7 so I can
>> > upgrade to oVirt 4.0. Currently my hosts already run el7, but my
>> > hosted-engine is still el6.
>> >
>> > I read
>> >
>> > https://www.ovirt.org/documentation/how-to/hosted-engine-host-OS-upgrade/
>> > but this is only about the hosts.
>> >
>> > I read https://www.ovirt.org/documentation/how-to/hosted-engine/, but it
>> > only mentions upgrade of the hosted-engine software, not the OS.
>> >
>> > I understood I can do a fresh hosted-engine install, and then import my
>> > storage domain to the new hosted engine, but:
>> >
>> > - Do I need to restore my hosted engine database? ( like described here:
>> >
>> > http://www.ovirt.org/develop/developer-guide/engine/migrate-to-hosted-engine/
>> > )
>>
>> You might not have to, if you only care about the imported VMs from your
>> storage. This will not keep other configuration, such as
>> users/roles/permissions
>> etc.
>>
>> > - Can I directly install hosted-engine 4.0 and then import the storage
>> > domain? Or should I install same hosted-engine version?
>>
>> AFAIK 4.0 engine can import 3.6 storage domains without problem.
>>
>> > - Do I first need another master storage domain or can I directly import
>> > my
>> > old master storage domain?
>>
>> No idea. Even if you do, you can create a small empty one and later remove
>> it.
>>
>> > - When importing the storage domain what is the risk it fails ( I have
>> > backups, but it would cost a day to restore all )
>>
>> No idea, but IIRC we got many successful reports and at most few failures
>> for this.
>>
>> > - How long would import take? few minutes or hours? ( I want to keep
>> > down
>> > time as low as possible ).
>>
>> Again no idea. Perhaps do some test?
>>
>> >
>> > Another option would be upgrade the OS ( with redhat-upgrade-tool ) or
>> > is
>> > this a path for disaster?
>>
>> Didn't work for us well, so we decided to not support it. If you decide to
>> try,
>> make sure you test carefully beforehand. From ovirt's POV:
>> 1. You'll need to handle postgresql upgrade.
>> 2. Right after OS upgrade, you'll still have (I think) el6 packages
>> of the engine. It will hopefully be in a good-enough state for upgrade
>> to 4.0, but we didn't test this.
>> 3. Specifically, if upgrade fails, rollback will most likely not work,
>> so you'll have to manually handle this - take a full vm backup and make
>> sure you can restore it.
>>
>> >
>> > I hope someone can tell me how I can smoothly upgrade my hosted-engine
>> > up to
>> > el7 and run oVirt 4.
>>
>> We are working on a tool/wizard to help with this process. It used to
>> work,
>> but at some point it was decided that one of the actions it does is risky
>> and was blocked, thus the tool is broken currently.
>>
>> You can invoke the tool by running: 'hosted-engine --upgrade-appliance'.
>> As noted above, this is currently broken.
>>
>> There are several open bugs about it, e.g.:
>>
>> https://bugzilla.redhat.com/show_bug.cgi?id=1319457
>> https://bugzilla.redhat.com/show_bug.cgi?id=1343425
>> https://bugzilla.redhat.com/show_bug.cgi?id=1343593 (closed, this is
>> what broke the tool)
>>
>> Basically, you can manually do what the tool is supposed to do:
>> 1. Make sure state is clean and stable (no running/pending storage
>> actions,
>> no VMs in the middle of migration etc), all clusters are compat level 3.6,
>> etc.
>> 2. Move to global maintenance
>> 3. backup the engine using engine-backup and keep the backup elsewhere
>> 4. Reinstall engine vm with el7 and 4.0 engine (the tool will use the
>> engine
>> appliance, you might too but not sure how exactly).
>> 5. Restore the backup and run engine-setup.
>> 6. If all looks ok, leave global maintenance.
>>
>> If you manually keep a full backup of the engine vm before step 4,
>> you might be able to restore this backup if there are problems.
>> Doing this in the provided tool is currently the main blocking issue
>> for it. Hopefully will be provided in 4.0.1.
>>
>> Best,
>> --
>> Didi
>
>
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