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From Wido den Hollander <w...@widodh.nl>
Subject Re: KVM VM snapshots any time soon ?
Date Wed, 05 Nov 2014 21:24:35 GMT


On 11/05/2014 10:18 PM, Mike Tutkowski wrote:
> Hey Wido,
> 
> Perhaps you know the answer to this:
> 
> My main interactions with KVM have been in the form of data disks.
> 
> I create a LUN on my SAN that gets passed to a VM as a data disk.
> 
> In this situation, how would a snapshot of such a disk work?
> 

The disk would be snapshotted, but at the same time the memory contents
of the VM would be written to a new disk/file.

> On XenServer and ESX, your data disk can be just a subset of the overall
> LUN and hypervisor snapshots create new virtual disks that are stored right
> next to the original ones on the same LUN.
> 
> I'm un-clear how this works in KVM.
> 

It would work about the same with KVM.

You can look into the "virsh save" command of libvirt to see what it does.

Wido

> Thanks!
> Mike
> 
> On Wed, Nov 5, 2014 at 2:01 PM, Wido den Hollander <wido@widodh.nl> wrote:
> 
>>
>>
>> On 11/05/2014 07:37 PM, Logan Barfield wrote:
>>> This is a feature we would like to see as well.
>>>
>>> Does KVM have native support for VM/Memory snapshotting?  If so what are
>>> the barriers to getting this implemented?
>>>
>>
>> KVM has the support, but there is a problem with the storage.
>>
>> Snapshotting a disk is simple, that's supported by QCOW2, LVM, RBD, etc.
>>
>> But when you want to snapshot a VirtualMachine you have to store the
>> memory contents somewhere.
>>
>> That is something that hasn't been worked out. Do you create a
>> additional 'disk' for storing the memory contents?
>>
>> That's the barriers I currently know for implementing it.
>>
>> Wido
>>
>>>
>>> Thank You,
>>>
>>> Logan Barfield
>>> Tranquil Hosting
>>>
>>> On Wed, Nov 5, 2014 at 1:20 PM, Andrija Panic <andrija.panic@gmail.com>
>>> wrote:
>>>
>>>> Anybody ?
>>>>
>>>> On 3 November 2014 15:23, Andrija Panic <andrija.panic@gmail.com>
>> wrote:
>>>>
>>>>> Hi guys,
>>>>>
>>>>> do we have any plans in some near future to imlement full VM KVM
>>>>> snapshots. So not single volume snaphost, but a reall VM snapshots. It
>> is
>>>>> already there for Xen/VMware, but not KVM.
>>>>>
>>>>> Any thoughts, ETA, or difficulties to implement this ?
>>>>> Any feedback greatly appriciated...
>>>>>
>>>>> Best,
>>>>>
>>>>>
>>>>> Andrija Panić
>>>>>
>>>>
>>>>
>>>>
>>>> --
>>>>
>>>> Andrija Panić
>>>> --------------------------------------
>>>>   http://admintweets.com
>>>> --------------------------------------
>>>>
>>>
>>
> 
> 
> 

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