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Re: [libvirt] [PATCHv2 06/20] snapshot: Add flag to enable creating checkpoints in live state



On 11/01/2012 10:22 AM, Peter Krempa wrote:
> The default behavior while creating external checkpoints is to pause the
> guest while the memory state is captured. We want the users to sacrifice
> space saving for creating the memory save image while the guest is live
> to minimize downtime.
> 
> This patch adds a flag that causes the guest not to be paused before
> taking the snapshot.
>  *include/libvirt/libvirt.h.in:
>     - add new paused reason: VIR_DOMAIN_PAUSED_SNAPSHOT
>     - add new flag for taking snapshot: VIR_DOMAIN_SNAPSHOT_CREATE_LIVE
>  *tools/virsh-domain-monitor.c:
>     - add string representation for VIR_DOMAIN_PAUSED_SNAPSHOT
>  *tools/virsh-snapshot.c:
>     - add support for VIR_DOMAIN_SNAPSHOT_CREATE_LIVE
>  *tools/virsh.pod:
>     - add docs for --live option added to use
>     VIR_DOMAIN_SNAPSHOT_CREATE_LIVE flag
> ---

> +++ b/src/libvirt.c
> @@ -17770,6 +17770,12 @@ virDomainSnapshotGetConnect(virDomainSnapshotPtr snapshot)
>   * running after the snapshot.  This flag is invalid on transient domains,
>   * and is incompatible with VIR_DOMAIN_SNAPSHOT_CREATE_REDEFINE.
>   *
> + * If @flags includes VIR_DOMAIN_SNAPSHOT_CREATE_LIVE, then the domain
> + * is not paused while creating the snapshot. This increases the size
> + * of the memory dump file, but reduces downtime of the guest while
> + * taking the snapshot. (Note: this feature works only with external
> + * checkpoints)

It is entirely feasible that we could do an internal snapshot without
pausing the guest, if future qemu gave us support; so our documentation
should be couched in terms of possible restrictions, not permanent
restrictions.

s/(Note: this feature works only with external checkpoints)/Some
hypervisors only support this flag during external checkpoints./

The virsh.pod wording is fine.

ACK with that change.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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