Re: [Xen-devel] [RFC V9 3/4] domain snapshot design: xl

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, Dec 16, 2014 at 02:32:56PM +0800, Chunyan Liu wrote:
> Changes to V8:
>   * xl won't manage snapshots, that means it won't maintain json files,
>     won't maintain snapshot chain relationship, and then as a result
>     won't take care of deleting snapshot and listing snapshots.
>   * remove snapshot-delete and snapshot-list interface
>   * update snapshot-revert interface
>   * update snapshot-create/revert implementaion
> 
> ===========================================================================
> 
> XL Design
> 
> 1. User Interface
> 
> xl snapshot-create:
>   Create a snapshot (disk and RAM) of a domain.
> 
>   SYNOPSIS:
>     snapshot-create <domain> [<cfgfile>] [--name <string>] [--live]
> 
>   OPTIONS:
>     --name <string>  snapshot name
>     --live           take a live snapshot
> 
>     If option includes --live, then the domain is not paused while creating
>     the snapshot, like live migration. This increases size of the memory
>     dump file, but reducess downtime of the guest.
> 
>     If option doens't include --name, a default name will be generated
>     according to the creation time.
> 
>     If specify @cfgfile, use cfgfile. (e.g. if --name specifies a name,
>     meanwhile there is name specified in cfgfile, name in cfgfile will
>     be used.)
> 
> 
> xl snapshot-revert:
>   Revert domain to status of a snapshot.
> 
>   SYNOPSIS:
>       snapshot-revert <domain> <cfgfile> [--running] [--force]
> 
>   OPTIONS:
>     --running        after reverting, change state to running
>     --force          try harder on risky reverts
> 
>     Normally, the domain will revert to the same state the domain was in while
>     the snapshot was taken (whether running, or paused).
> 
>     If option includes --running, then overrides the snapshot state to
>     guarantee a running domain after the revert.
> 
> 
> 
> 2. cfgfile syntax
> 
> #snapshot name. If user doesn't provide a VM snapshot name, xl will generate
> #a name automatically by the creation time.
> name=""
> 
> #snapshot description. Default is NULL.
> description=""
> 
> #memory location. This field should be filled when memory=1. Default is NULL.
> memory_path=""
> 
> #disk snapshot information
> #For easier parse config work, reuse disk configuration in xl.cfg, but
> #with different meanings.
> #disk syntax meaning: 'external path, external format, target device'
> 
> #e.g. to specify exernal disk snapshot, like this:
> #disks=['/tmp/hda_snapshot.qcow2,qcow2,hda',
>         '/tmp/hdb_snapshot.qcow2,qcow2,hdb',]
> 
> #e.g. to specify internal disk snapshot, like this:
> disks=[',,hda',',,hdb',]
> 

How is snapshot chain represented with this syntax? Does xl not need to
know about the chain? (Note, this is different than managing the chain)

Wei.

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