[CentOS-virt] proper way to snapshot

Peter Peltonen

peter.peltonen at gmail.com
Fri Apr 27 08:23:18 UTC 2012


Hi,

On Fri, Apr 27, 2012 at 12:48 AM, aurfalien <aurfalien at gmail.com> wrote:
> On Apr 26, 2012, at 2:24 PM, Nux! wrote:
>
>> On 26.04.2012 19:21, aurfalien wrote:
>>> On Apr 26, 2012, at 2:15 PM, Nux! wrote:
>>>
>>>> On 26.04.2012 19:12, aurfalien wrote:
>>>>> On Apr 26, 2012, at 1:54 PM, Nux! wrote:
>>>>>
>>>>>> On 26.04.2012 18:23, aurfalien wrote:
>>>>>>> Hi,
>>>>>>>
>>>>>>> While there are a few howtos floating around, what is the
>>>>>>> standard
>>>>>>> way to snapshot guests?
>>>>>>>
>>>>>>> I went through and converted from raw to pre allocated meta data
>>>>>>> qcow2 images for this purpose.
>>>>>>>
>>>>>>> Some howtos suggest to do an xml snapshot file as so;
>>>>>>>
>>>>>>> <domainsnapshot>
>>>>>>> <name>UbuntuServer_10.10-16032011</name>
>>>>>>> <description>Snapshot of OS install and updates</description>
>>>>>>> </domainsnapshot>
>>>>>>>
>>>>>>> And then to run as so;
>>>>>>>
>>>>>>> virsh snapshot-create UbuntuServer_10.10
>>>>>>> UbuntuServer_10.10-ss.xml
>>>>>>>
>>>>>>> Seems a bit over kill.
>>>>>>>
>>>>>>> I was thinking more along the lines of this;
>>>>>>>
>>>>>>> qemu-img snapshot -c $date $filename
>>>>>>>
>>>>>>> qemu-img convert -f qcow2 -O qcow2 -s $date $filename
>>>>>>> $filename-$date
>>>>>>>
>>>>>>> Or something like this.Anyways, hoping to see how you all are
>>>>>>> doing
>>>>>>> this for best practice sort of thing.
>>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> I just use LVM snapshots; it's the fastest, most reliable way I
>>>>>> could
>>>>>> come with.
>>>>>
>>>>> Hi,
>>>>>
>>>>> I don't have LVMs.
>>>>>
>>>>> But if I did, would it be possible to only snapshot a directory or
>>>>> will it snapshot the entire file system?
>>>>
>>>> Assuming you use LVM on the host to provide the virtual machine with
>>>> a
>>>> (virtual) HDD, then snapshotting that will obviously be (virtual)
>>>> disk-wise.
>>>
>>> I used a simple non LVM partitioning scheme.
>>>
>>> Can I do directory based snapshots in LVM or is it the entire FS?
>>>
>>> I can re implement or redo my host to use LVM.
>>>
>>> - aurf
>>> _______________________________________________
>>> CentOS-virt mailing list
>>> CentOS-virt at centos.org
>>> http://lists.centos.org/mailman/listinfo/centos-virt
>>
>> Aurf,
>>
>> LVM is filesystem level, not directory level. What I'd recommend is to
>> reinstall and use LVM, make a couple of volumes for / and swap and leave
>> the rest for virtual machines.
>
> The real problem with this is that snapshots are still on the local box and I don't have a SAN.
>
> With KVM based qcow snaps, I can do snaps over NFS.

You can copy LVM snapshots easily to some other location with dd (=
create image file of the snapshot LVM volume) that you can restore
where ever you like using dd again.

Regards,
Peter



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