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From Amit Das <amit....@cloudbyte.com>
Subject Re: Question regarding Quiesce VM feature in ACS 4.3 wrt XEN hypervisor
Date Fri, 18 Jul 2014 04:10:03 GMT
thanks Mike. I shall have a look at the implementation details.

Will be looking forward to any documentation if any.

Regards,
Amit
*CloudByte Inc.* <http://www.cloudbyte.com/>


On Fri, Jul 18, 2014 at 8:58 AM, Mike Tutkowski <
mike.tutkowski@solidfire.com> wrote:

> Hi Amit,
>
> I don't really know these details in depth (NetApp added this feature in
> v4.3).
>
> I have CCed David La Motta from NetApp. Perhaps he can explain more than I
> did.
>
> I do know that from a storage standpoint you don't have to implement
> anything if you just want to ignore this feature.
>
> The idea is that if you want to support this feature, then you (I think)
> need to implement a snapshot strategy (a CS interface) (or perhaps use the
> one NetApp implemented).
>
> The overall idea is that this works for NFS if you want to take a snapshot
> of a file on a share and you want to try to take the snapshot when the VM
> is in a quiesced state.
>
> Step one is the VM gets quiesced.
>
> Step two is a hypervisor snapshot is taken (which leads to a new (delta)
> file on the XenServer Shared (NFS) Storage Repository).
>
> Step three is you can have your storage plug-in notified and it can take a
> snapshot of this new file.
>
> Step four is cleanup related on the hypervisor: The VM snapshot is deleted
> and the delta file can be merged back into its parent by XenServer.
>
> I think the reason we take a hypervisor snapshot is so we can then quickly
> un-quiesce the VM and asynchronously have the storage plug-in take its
> snapshot. Then we can later go back and delete the hypervisor snapshot, so
> this virtual disk can have its parent and delta files merged back together.
>
> Talk to you later,
> Mike
>
>
> On Wed, Jul 16, 2014 at 9:31 AM, Amit Das <amit.das@cloudbyte.com> wrote:
>
>> W.r.t hypervisor specific snapshots :
>> - why is this snapshot required when a VM or its hypervisor supports
>> quiesce operation.
>> - what exactly happens during hypervisor snapshot ? Can this step be
>> excluded.
>>
>>
>> On Wednesday, July 16, 2014, Mike Tutkowski <mike.tutkowski@solidfire.com>
>> wrote:
>>
>>> This line at the bottom of my previous e-mail was redundant...I meant to
>>> remove it before sending:
>>>
>>> A vendor snapshot can be created of the hypervisor snapshot file, then
>>> CS can automatically delete
>>>
>>>
>>> On Wed, Jul 16, 2014 at 8:10 AM, Mike Tutkowski <
>>> mike.tutkowski@solidfire.com> wrote:
>>>
>>>> I believe this is what happens:
>>>>
>>>> * The VM gets quiesced.
>>>> * Hypervisor snapshots are taken of all VM disks (so a new delta file
>>>> shows up on each applicable SR).
>>>>  * The applicable storage plug-in can be invoked to take a
>>>> vendor-specific snapshot of a given hypervisor snapshot delta file.
>>>> * Once the storage plug-in is done, CS can delete the hypervisor
>>>> snapshot delta file(s) that was/were created.
>>>>
>>>> A couple notes about this:
>>>>
>>>> * Since you are taking a vendor-side snap of a particular file, this
>>>> relates to NFS.
>>>>
>>>> * I believe all disks of the VM need to be supported by the same
>>>> storage vendor (i.e. if the root and data disks are on different SRs, each
>>>> SR needs to be supported by the storage of the same backend vendor)
>>>>
>>>> A vendor snapshot can be created of the hypervisor snapshot file, then
>>>> CS can automatically delete
>>>>
>>>> On Wednesday, July 16, 2014, Punith S <punith.s@cloudbyte.com> wrote:
>>>>
>>>>> hi,
>>>>>
>>>>> while i was referring the ACS 4.3 doc for VM snapshot,
>>>>> i see a feature Quiesce VM supported only by vmware hypervisor if the
>>>>> cloudstack default primary storage is used,
>>>>> but it also mentions that Quiesce VM can be supported if you are using
>>>>> a
>>>>> third party primary storage plugin, the quiesce operation is provided
>>>>> by
>>>>> plugin implementation!
>>>>>
>>>>> is Quiesce VM is a limitation of  XEN hypervisor or is it not
>>>>> implemented
>>>>> by xen agent in cloudstack ?
>>>>>
>>>>> how is third party primary storage plugin related to hypervisor
>>>>> feature ?
>>>>>
>>>>> --
>>>>> regards,
>>>>>
>>>>> punith s
>>>>> cloudbyte.com
>>>>>
>>>>
>>>
>>>
>>> --
>>> *Mike Tutkowski*
>>> *Senior CloudStack Developer, SolidFire Inc.*
>>> e: mike.tutkowski@solidfire.com
>>> o: 303.746.7302
>>> Advancing the way the world uses the cloud
>>> <http://solidfire.com/solution/overview/?video=play>*™*
>>>
>>
>>
>> --
>> Regards,
>> Amit
>> *CloudByte Inc.* <http://www.cloudbyte.com/>
>>
>>
>
>
> --
> *Mike Tutkowski*
> *Senior CloudStack Developer, SolidFire Inc.*
> e: mike.tutkowski@solidfire.com
> o: 303.746.7302
> Advancing the way the world uses the cloud
> <http://solidfire.com/solution/overview/?video=play>*™*
>

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