[CentOS-virt] proper way to snapshot
aurfalien
aurfalien at gmail.com
Fri Apr 27 09:53:02 EDT 2012
Hi,
On Apr 27, 2012, at 4:23 AM, Peter Peltonen wrote:
> 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.
After some experiment with qcow vs raw, I think raw is more stable and a tad fatser even if you pre allocate the metadata for your qcow images.
So, I will opt for LVMs.
Do you have a best practice in terms of ratio of snapshot to live FS?
In other words, should my LVM snapshot partition be 1:1 with my live FS size or 2/3 the size of bigger?
This will be based off a Raid 1 system.
- aurf
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