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Re: KVM NFS template image

Hi Andrija,

That is precisely the step I went through.

However the template was not cleaned up after expected interval when no other volume have it as a backing image.

On 11/22/2018 12:53 PM, Andrija Panic wrote:
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):

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:

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 ?


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).


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

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

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
2018-11-19 19:37:59,643 DEBUG [c.c.h.o.r.Ovm3HypervisorGuru]
(StorageManager-Scavenger-2:ctx-f9dd338d) (logid:9ae40975)
getCommandHostDelegation: class
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.


On Mon, 19 Nov 2018 at 19:11, Andrija Panic <andrija.panic@xxxxxxxxx>
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>

Developers please correct me... but as far as I remember there is a
garbage collector which does remove the templates from primary storage
they are not needed (i.e. have no more "child VMs"). This is
controlled by
the global setting "storage.template.cleanup.enabled".

Dag Sonstebo
Cloud Architect

On 16/11/2018, 22:51, "ran huang" <ran.huang134@xxxxxxxxx> wrote:

      Hi Andrija,

      Thanks for the clarification and quick response


      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
      > specific template). All VMs have this templates qcow2 as baking
      > 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
      > terminology)
      > you can have i.e. 100 VMs all linking (having it's backing
to a
      > template qcow2 file.
      > So in other words, it's not supposed to be removed.
      > Does this make sense?
      > Cheers

Amadeus House, Floral Street, London  WC2E 9DPUK

On Fri, 16 Nov 2018 at 22:38, ran huang <ran.huang134@xxxxxxxxx>
      >> Greetings All,
      >> For qcow2 format images, when creating a new VM in KVM, the
      >> image is copied from secondary storage to primary storage, and
      >> volume image is created with the template image as a backing
      >> But when I break this backing chain on primary(expunge VM or
revert to a
      >> snapshot previously created on the root volume image), the
      >> image is not deleted.
      >> Might I ask how is the template image going to be cleaned from
      >> primary storage?
      >> addendum:
      >> CS ver 4.9.2 on CentOS 7.2
      >> regards,
      >> Ran


Andrija Panić