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From Wido den Hollander <w...@widodh.nl>
Subject Re: KVM VM snapshots any time soon ?
Date Thu, 06 Nov 2014 07:59:00 GMT


On 11/05/2014 10:26 PM, Mike Tutkowski wrote:
> When you say the disk would be snapshotted, do you mean from the point of
> view of the SAN or from the point of view of the hypervisor?
> 

Hypervisor. QCOW2 files support snapshots, so does RBD.

When using iSCSI we usually create a VG on top of the LUN and then we
can snapshot each LV which is mapped to a Instance.

> A SAN snapshot is no problem. I'm mainly curious to see how this would work
> for a hypervisor snapshot.
> 
> Thanks!
> 
> On Wed, Nov 5, 2014 at 2:24 PM, Wido den Hollander <wido@widodh.nl> wrote:
> 
>>
>>
>> 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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