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Re: KVM NFS template image


Hi Run,

not sure what you mean  (I did not quite understand your explanation) - but
here is an exercise from my side (just done it):

https://pasteboard.co/HOowNao.png

Check the image - explanation below:


Centos55 minimal (builtin) template, spin new VM:
--- new volume created with UUID/PATH (name on NFS files
system): 021e8602-235b-4e0d-b9e4-04f0ff46399f
--it's backing file: backing file:
/mnt/63a3ae7b-9ea9-3884-a772-1ea939ef6ec3/93682641-e7f6-11e8-8f64-089e01d943be

Create snapshots via GUI - there is qcow2 snapshots created, whole snapshot
copied over (converted via qemu-img - "ps aux | grep qemu-img") tool to
Secondary NFS Storage - and snapshot REMOVED from original volume on
Primary NFS Storage (qemu-img snapshot -l
021e8602-235b-4e0d-b9e4-04f0ff46399f shows zero snaps after ACS has
finished creating snapshots)
Volume still points to it's backing file - no changes so far (as expected)

Then I restore volume from snapshots.
CloudStack will (my conclusions from the exercise), remove original volume
on NFS Primary Storage (021e8602-235b-4e0d-b9e4-04f0ff46399f), then it will
copy back (convert via qemu-img) a qcow2 file from Secondary Storage back
to Primary Storage - but it will use SAME NAME, so you again see
021e8602-235b-4e0d-b9e4-04f0ff46399f on your NFS mount point.

This time when you check the image with qemu-img info - it will show it has
NO backing file at all - since it's brand new volume/qcow2 image created
(as a copy fom Secondary Storage)

that is how it works

I assume the template will be again cleaned-up/removed from Primary Storage
if no other VMs/volume use it as it's backing (parent) image.

Makes sense ?

Cheers

On Thu, 22 Nov 2018 at 21:18, ran huang <ran.huang134@xxxxxxxxx> wrote:

> Thanks Andrija, just tested myself with expunge and works as expected.
>
> However, for KVM, when I revert a qcow disk from snapshot, which removes
> the backing chain to template, the template will not be removed.
>
> So it seems like despite the qcow disk is no longer backed by the
> template, the template will still consider the disk as its children in
> this case(revert from snapshot).
>
> regards,
> Ran
>
> On 11/19/2018 10:43 AM, Andrija Panic wrote:
> > new template, deployed new VM, destroyed VM (with Exunge option)...
> >
> > up to 120sec later... (storage.cleanup.interval=120 sec,  global config
> > option)
> >
> > 2018-11-19 19:35:59,525 DEBUGStorage pool garbage collector found 1
> > templates to clean up in storage pool: Primary-storage - NFS
> > 2018-11-19 19:35:59,525 DEBUG [c.c.s.StorageManagerImpl]
> > (StorageManager-Scavenger-1:ctx-2c88c8e0) (logid:040f4ad1) Storage pool
> > garbage collector has marked template with ID: 219 on pool 4 for garbage
> > collection
> >
> > Another  120sec later... (storage.cleanup.delay=120sec)
> >
> > 2018-11-19 19:37:59,598 DEBUG [c.c.s.StorageManagerImpl]
> > (StorageManager-Scavenger-2:ctx-f9dd338d) (logid:9ae40975) Storage pool
> > garbage collector found 1 templates to clean up in storage pool:
> > Primary-storage - NFS
> > ...
> > 2018-11-19 19:37:59,638 DEBUG [c.c.t.TemplateManagerImpl]
> > (StorageManager-Scavenger-2:ctx-f9dd338d) (logid:9ae40975) Evicting
> > TmplPool[37-219-4-563ea0f5-5164-4ac4-a183-728f418269b7]
> > 2018-11-19 19:37:59,643 DEBUG [c.c.h.o.r.Ovm3HypervisorGuru]
> > (StorageManager-Scavenger-2:ctx-f9dd338d) (logid:9ae40975)
> > getCommandHostDelegation: class
> com.cloud.agent.api.storage.DestroyCommand
> > ...
> > 2018-11-19 19:37:59,665 DEBUG [c.c.t.TemplateManagerImpl]
> > (StorageManager-Scavenger-2:ctx-f9dd338d) (logid:9ae40975) Successfully
> > evicted template andrija-test-tmpl from storage pool null
> >
> > template "andrija-test-tmpl" deleted...
> >
> > Hope that helps Run.
> >
> > Cheers
> > Andrija
> >
> > On Mon, 19 Nov 2018 at 19:11, Andrija Panic <andrija.panic@xxxxxxxxx>
> wrote:
> >
> >> True (at least I'm sure for SolidFire) - but I believe in general also
> >> (will test this now...)
> >>
> >> On Mon, 19 Nov 2018 at 18:51, Dag Sonstebo <Dag.Sonstebo@xxxxxxxxxxxxx>
> >> wrote:
> >>
> >>> Developers please correct me... but as far as I remember there is a
> >>> garbage collector which does remove the templates from primary storage
> once
> >>> they are not needed (i.e. have no more "child VMs"). This is
> controlled by
> >>> the global setting "storage.template.cleanup.enabled".
> >>>
> >>> Regards,
> >>> Dag Sonstebo
> >>> Cloud Architect
> >>> ShapeBlue
> >>>
> >>>
> >>> On 16/11/2018, 22:51, "ran huang" <ran.huang134@xxxxxxxxx> wrote:
> >>>
> >>>      Hi Andrija,
> >>>
> >>>      Thanks for the clarification and quick response
> >>>
> >>>      regards,
> >>>      Ran
> >>>
> >>>      On 11/16/2018 02:15 PM, Andrija Panic wrote:
> >>>      > Hi Ran,
> >>>      >
> >>>      > templates stays on Primary Storage "forever", at least for NFS
> >>> (they are
> >>>      > moved from Secondary to Primary when you deploy a very first VM
> from
> >>>      > specific template). All VMs have this templates qcow2 as baking
> >>> (parent)
> >>>      > image.
> >>>      >
> >>>      > This template is a qcow2 copy of a file from Secondary Storage -
> >>> and is
> >>>      > considered a "parent" image, from which all child images  (VM
> >>> volumes) are
> >>>      > created - as you stated baking file (qcow linked clones, in
> official
> >>>      > terminology)
> >>>      >
> >>>      > you can have i.e. 100 VMs all linking (having it's backing
> file...)
> >>> to a
> >>>      > template qcow2 file.
> >>>      > So in other words, it's not supposed to be removed.
> >>>      >
> >>>      > Does this make sense?
> >>>      >
> >>>      > Cheers
> >>>      >
> >>>      >
> >>>      >
> >>>
> >>> Dag.Sonstebo@xxxxxxxxxxxxx
> >>> www.shapeblue.com
> >>> Amadeus House, Floral Street, London  WC2E 9DPUK
> >>> @shapeblue
> >>>
> >>>
> >>>
> >>>> On Fri, 16 Nov 2018 at 22:38, ran huang <ran.huang134@xxxxxxxxx>
> wrote:
> >>>      >
> >>>      >> Greetings All,
> >>>      >>
> >>>      >> For qcow2 format images, when creating a new VM in KVM, the
> >>> template
> >>>      >> image is copied from secondary storage to primary storage, and
> the
> >>> root
> >>>      >> volume image is created with the template image as a backing
> file.
> >>>      >>
> >>>      >> But when I break this backing chain on primary(expunge VM or
> >>> revert to a
> >>>      >> snapshot previously created on the root volume image), the
> template
> >>>      >> image is not deleted.
> >>>      >>
> >>>      >> Might I ask how is the template image going to be cleaned from
> the
> >>>      >> primary storage?
> >>>      >>
> >>>      >>
> >>>      >> addendum:
> >>>      >> CS ver 4.9.2 on CentOS 7.2
> >>>      >>
> >>>      >> regards,
> >>>      >> Ran
> >>>      >>
> >>>      >
> >>>
> >>>
> >>>
> >>>
> >> --
> >>
> >> Andrija Panić
> >>
> >
>
>

-- 

Andrija Panić