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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 at gmail.com>

> 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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