openstack team mailing list archive

[Yufang Zhang <yufang521247@xxxxxxxxx>]

Does it make sense to shutdown instance before doing snaphotting, and then
make a lvm snaphot of instance disk. This would be safe for instance though
it‘s not some sort of 'live snaphot'.

2012/7/16 Boris Filippov <bfilippov@xxxxxxxxxxxxxxxx>

> Current snapshot implementation for libvirt driver doesn't support
> snapshotting for everything except qcow2 (as i remember, because virDomainManagedSave
> will fail on everything except qcow2). So, maybe we can discuss it here.
> This for sure can be implemented for lvm using lvm snapshots but it will be
> unsafe doing snapshot on alive instance. LVM is much like raw right now and
> raw doesn't support snapshots with current logic too.
>
>
> 2012/7/16 Li Wang <foxban@xxxxxxxxx>
>
>> hi, all
>>
>>         As LVM backend image support was introduced in the trunk version
>> of nova, is there any plan to support snapshot of the LVM backend image?
>>
>>         I am using libvirt and Xen, with lvm as the instance image
>> backend.
>>
>>         There are two issues when creating snapshot.
>>
>>         1. when calling managedSave, libvirt complained there's no
>> supported function by the driver.
>>
>>                 "libvirtError: this function is not supported by the
>> connection driver: virDomainManagedSave"
>>
>>         2. when actually creating snapshot, libvirt calls qemu-img, which
>> does not support lvm.
>>
>>         As a result, snapshot status is always 'queue', and actually it's
>> failed.
>>
>>
>>         For issue 1, it seems that libvirt does not support "save" or
>> similar functions for xen, some modifications to the libvirt Xen driver
>> maybe help?
>>
>>         For issue 2, I think the snapshot action should call lvm related
>> command but not qemu-img when using lvm.
>>
>>         For example:    lvcreate --snapshot ..........
>>
>>
>>         Further discussions and replies are welcome.
>>
>>         Thanks all
>>
>>
>> Regards
>>
>>
>> Wang Li
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