[ovirt-users] Autostart VMS

Fri Apr 8 22:09:38 UTC 2016

You are welcome.  I haven't filed a bug for it yet but will be glad to
do so or would it be a Feature request?  I assume I go to the oVirt bug
tracker site.
On Sat, 2016-04-09 at 01:06 +0300, Nir Soffer wrote:
> On Sat, Apr 9, 2016 at 12:07 AM, Brett I. Holcomb 
> om> wrote:
> > 
> > On Fri, 2016-04-08 at 21:50 +0300, Nir Soffer wrote:
> > 
> > On Fri, Apr 8, 2016 at 9:33 PM, Brett I. Holcomb 
> > com>
> > wrote:
> > 
> > On Fri, 2016-04-08 at 19:25 +0300, Nir Soffer wrote:
> > 
> > On Fri, Apr 8, 2016 at 7:17 PM, Brett I. Holcomb 
> > com>
> > wrote:
> > 
> > On Fri, 2016-04-08 at 11:31 +0200, Martin Sivak wrote:
> > 
> > Hi,
> > 
> > 
> > I set highly available on, did not pin to any host, and also set
> > the
> > watchdog which should reset if they go down but I'm not sure that
> > will start
> > them if the host comes up and the VMs are not running.  I'll look
> > at the CLI
> > first.
> > 
> > 
> > The engine will try to keep the VM running. So if one host goes
> > down,
> > it will restart the VM on some other host automatically. We will
> > also
> > migrate the VM (or some other to free resources) when the current
> > host
> > gets too loaded. We do not require any migration addons, it just
> > works. But of course we have usually more hosts in a cluster to
> > make
> > this possible.
> > 
> > I do not really remember what happens when all hosts are restarted
> > (power outage) though as that is quite special case.
> > 
> > Regards
> > 
> > --
> > Martin Sivak
> > SLA / oVirt
> > 
> > 
> > 
> > Thanks.  I only have one host so who knows what will happen.  I'm
> > working on
> > a script that will basically emulate what VMware does - start VMS
> > in a given
> > order at startup of the host/engine.  I'll also file a feature
> > request.
> > 
> > 
> > Why do you care about the order?
> > 
> > Isn't it enough to restart all the vms after a host was restarted?
> > 
> > Nir
> > 
> > 
> > Does the Engine start all VMs after the host is powered up and the
> > engine
> > running if I set a watchdog on a VM?  I know it will try to restart
> > the VM
> > if it goes down once oVirt is up and running.   If it will start
> > the VMs at
> > reboot time that helps.
> > 
> > 
> > I think only HA vms are restarted. Adding Michal to add more info
> > on this.
> > 
> > 
> > The reason for the order is that you need some servers such as DNS,
> > file
> > servers, up first before other systems can resolve addresses or
> > mount
> > shares.  For Windows you need domain controllers running before the
> > other
> > windows systems that are part of the domain.  For applications such
> > as Lotus
> > Notes the servers had to come up in the correct order.
> > 
> > 
> > Lets say you have a way to order the vms when some vms are down.
> > 
> > What will happen to when dns, file servers or domain controller
> > will crash?
> > Do you have to restart all the vms depending on them or they can
> > recover and detect that vm they depend on were restarted?
> > 
> > Seems that what you need is a systemd for your data center - every
> > host define the host it depends on, and the system generate the
> > correct order to start the vms, starting vms in the same time when
> > possible.
> > 
> > Please reply also to the list, this thread may be useful to others.
> > 
> > Nir
> > 
> > 
> > Hopefully this will go to the list as i"ve been making sure users at o
> > virt.org
> > is in the To field.
> > 
> > I think we need to make sure we distinguish between the start up
> > phase and
> > the running phase which is what happens after everyone is up and
> > running
> > happily.  Based on my experience the crash of a server is
> > considered
> > separately from startup.
> > 
> > As mentioned in my response to the list to someone else's comment
> > the
> > startup sequence is the same as people flipping switches on
> > physical servers
> > following a documented procedure to start or shutdown a datacenter
> > as we did
> > in the "old days".  With physical boxes we had to shutdown/startup
> > manually
> > and we did it in a sequence that we had written down.  With
> > virtualization
> > and since we had VMware we could automate that process so as we
> > spun up the
> > hosts VMware started spinning up the guests in the order specified
> > so we got
> > our DNS boxes up first, then others.  For Active Directory we
> > started the
> > domain controllers first, then other servers such as file servers,
> > application servers in the sequence needed for the applications to
> > run.
> > 
> > Crashing of DNS, File Server, Domain Controllers crashing after the
> > datacenter is up and running is handled (or should be) by
> > redundancy of
> > servers or process the service provides.  You have multiple DNS
> > servers and
> > the resolver will try the secondary/tertiary/whatever if the
> > primary is
> > down.  File servers are the same.  For Gluster, CephFS, MS DFS you
> > have (or
> > should have setup) the ability to keep running if one of the
> > servers goes
> > down.  A redundant file server setup will handle a server
> > crash.  For Domain
> > Controllers you should have at least two (we had six in our
> > environment) and
> > when one goes down the others keep the domain running by shifting
> > the
> > services to others and continuing to provide authentication,
> > etc.  Generally
> > what we did when a domain controller crashed is fix it if possible
> > and if it
> > was not fixable pull it's pieces out of the domain and spin up a
> > new one.
> > Same for DNS or file servers.  When they go down find out why, fix
> > it or
> > replace the server, and get the service redundant again.  Also,
> > oVirt has
> > the watchdog function so if a VM goes down it will try and restart
> > it.  If
> > it can't restart then we're dealing with a crashed server which we
> > should
> > have provided for in our data center design.
> > 
> > My wish is to have oVirt allow us to do what VMware does and allow
> > us to say
> > start/don't start these servers up in the order I specify so that
> > when the
> > Engine is ready it looks at the list and begins turning on VMs in
> > the order
> > specified.  Shutdown is done in the reverse order).  For large
> > datacenters
> > with many VMS manual startup is a pain.  Once it's running rely on
> > good
> > practices of having redundant servers (i.e. more than one DNS),
> > file servers
> > that can handle the failure of a server, multiple domain
> > controllers which
> > is not something we need to burden oVirt with.  Handling of
> > failures needs
> > to be done by the people in charge who are supposed to design the
> > data
> > center based on their risk/cost analysis.
> > 
> > If I  understand what you said - I'm not sure we have to define a
> > dependancy
> > list where we define dependancies like we would with systemd or a
> > package
> > manger.  It doesn't need to be complex since just a simple list of
> > priority:
> > VM id/name pairs will work. All we need is to be able to say "start
> > these
> > VMs when the Engine is ready".  The order or dependency is set by
> > where I
> > put the VM in the list.  If it's at the top start it first, then
> > move to the
> > second one, and so on.  There can be settings for delay between
> > starting VMs
> > and how long to wait for a VM to come up before assuming it's dead
> > and
> > moving on to the next.  Tasking oVirt with the job of figuring VM
> > dependancies would be a nightmare for oVirt and whoever had to
> > program it
> > .  We as data center administrators should be handling that
> > task.  Yes,
> > we manually set the list but trying to automate a dependancy chain
> > would be
> > pretty difficult.
> > 
> > I envision a web admin portal GUI where we define a simple list of
> > VMs that
> > we want the Engine to autostart. We need to be able to move them
> > up/down the
> > list.  The list is stored somewhere for the Engine (database?,
> > whatever else
> > the Engine has as storage areas - not really familiar with the
> > Engine
> > internals) and when the Engine is up and ready to start VMs it
> > retrieves the
> > list and starts at the first VM in the list and starts it, waits
> > some time
> > (0-?? seconds), and then moves on to the next one.  If the VM
> > hasn't started
> > in the set time the Engine moves on to the next one.
> > 
> > Note that Microsoft's Hyper-V also provides automatic VM startup
> > but it is
> > done on a VM level where you just tell the VM to start whenthe
> > Hypr-V
> > starts.  If you want sequencing you have to set time
> > delays.  Auto  start up
> > is better than nothing but Hyper-V is a nightmare trying to
> > sequence VMs.
> > 
> > I think VMware did it right in allowing both autostart and being
> > able to
> > sequence the startup of VMS so it's host independent.  As
> > information VMware
> > also allowed delays between VM startups as does Hyper-V.
> Thanks for the detailed description.
> 
> Did you file a bug for this feature?
> 
> Adding Moran and Doron.
> 
> Nir
> 
> > 
> > On Wed, Apr 6, 2016 at 9:10 PM, Brett I. Holcomb 
> > com>
> > wrote:
> > 
> > On Wed, 2016-04-06 at 13:42 -0400, Adam Litke wrote:
> > 
> > On 06/04/16 01:46 -0400, Brett I. Holcomb wrote:
> > 
> > In VMware we could setup guests to autostart when the host started
> > and
> > define the order.  Is that doable in oVirt?  The only thing I've
> > seen
> > is the watchdog and tell it to reset but nothing that allows me to
> > define who starts up when and if they autostart.  I assume it's
> > there
> > but I must be missing it or haven't found it in the web portal.
> > 
> > 
> > In oVirt guests aren't tied to a host by default (although you can
> > set
> > them to run only on a specific host if you want).  The closest
> > thing I
> > can think of would be the High Availability features (VM->Edit).
> > oVirt will try to restart highly available VMs if they go
> > down.  You
> > can also set the priority for migration and restart in that pane.
> > Hopefully a combination of host pinning and the  high availability
> > settings will get you close enough to where you want to be.
> > 
> > Otherwise, you could always do some scripting with the ovirt REST
> > API
> > using the SDK or CLI.
> > 
> > 
> > If you had the VMware migration extra add-on you could have hosts
> > move as
> > needed so they were not tied to any host either but we could set a
> > startup
> > order and specify auto, manual so that once the host started the
> > VMs were
> > brought up as specified no matter what host they were running on.
> > 
> > I am running hosted-engine deployment with the Engine VM on the
> > host.
> > 
> > I set highly available on, did not pin to any host, and also set
> > the
> > watchdog which should reset if they go down but I'm not sure that
> > will start
> > them if the host comes up and the VMs are not running.  I'll look
> > at the CLI
> > first.
> > 
> > It would be nice if oVirt added this feature as it's really
> > required for
> > large installations and is a help for any size installation, even
> > small
> > ones.
> > 
> > 
> > 
> > 
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> > 
> > 
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> > 
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