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Re: Question about instance volumes


Thanks for the answer.

May I ask why are there some instances that do have a golden image and some
that do not?

All the instances come from a template so I wonder why this varies.

Also why would the golden image be deleted by the Cloudstack scavenger? I
have an Instance failing to boot because it's backing file was deleted by
the scavenger.

Thanks,

On Mon, Apr 23, 2018 at 4:43 AM, Andrija Panic <andrija.panic@xxxxxxxxx>
wrote:

> As Ivan explained, when there is brand new template used, ACS will copy it
> from Secondary Storage to Primary Storage, this image will become "parent"
> / backing / gold image, and is locked as Read Only. Any new VM will have
> it's volume "linked" as child image to this parent image.
> This is done to
>
> 1) Save space (imagine 100GB template), and you deploy 100 VMs = maybe
> 101GB totally used really...(until you write some new data - it is written
> to child images) vs 10000GB if it would be separate images.
>
> 2) This also brings some performance benefits, since you read from 1 x
> 100GB image, not from 100x 100GB images...
>
> Cheers
>
>
> On 23 April 2018 at 03:59, Ivan Kudryavtsev <kudryavtsev_ia@xxxxxxxxx>
> wrote:
>
> > Hi.
> >
> > When you create a VM from a template then ACS doesn't copy the template
> to
> > a new root image, but creates it thin, pointing the volume to the
> template
> > as a backing store device.
> >
> > пн, 23 апр. 2018 г., 8:16 Felipe Arturo Polanco <
> felipeapolanco@xxxxxxxxx
> > >:
> >
> > > Hello,
> > >
> > > I am seeing a behavior that I would like to ask about.
> > >
> > > I have some instances that instead of having a normal qcow2 disk file,
> > have
> > > a qcow2 file that points to another backing store file.
> > >
> > > eg:
> > >
> > > <disk type='file' device='disk'>
> > >       <driver name='qemu' type='qcow2' cache='none'/>
> > >       <source file='/mnt/ps4/c6a79f0b-60b2-419c-98af-6ae854f88ad1'/>
> > >       <backingStore type='file' index='1'>
> > >         <format type='raw'/>
> > >         <source file='/mnt/ps4/ddc78c68-47b2-43ef-9109-4c91ebb8bda5'/>
> > >         <backingStore/>
> > >       </backingStore>
> > >       <target dev='vda' bus='virtio'/>
> > >       <serial>c6a79f0b60b2419c98af</serial>
> > >       <alias name='virtio-disk0'/>
> > >       <address type='pci' domain='0x0000' bus='0x00' slot='0x04'
> > > function='0x0'/>
> > >     </disk>
> > >
> > > I am reading online that this is seen when there is a snapshot of
> another
> > > disk file, but I have no snapshots, just a regular Linux server that I
> > > created through the Cloudstack UI.
> > >
> > > Any idea of why this would happen? Not all Instances have this backing
> > > storage file.
> > >
> > > Thanks,
> > >
> >
>
>
>
> --
>
> Andrija Panić
>