Re: [Qemu-devel] [PATCH v4 3/6] add backup related monitor commands

[Dietmar Maurer]

> > Anyways, and additional RPC layer always adds overhead, and It can be
> completely avoided.
> > Maybe not much, but I want to make backup as efficient as possible.
> 
> The drawbacks outweight the performance advantage:

not for me.

> 1. QEMU can neither backup nor restore without help from the management
>    tool.  

Backup works perfectly with the current patches. You can easily trigger a 
backup using 
a HMP command. This is not really important, but works.

> This is a strong indicator that the backup archive code should
>    live outside QEMU.  I doesn't make sense for proxmox, oVirt,
>    OpenStack, and others to each maintain their backup archive code
>    inside qemu.git, tied to QEMU's C codebase, release cycle, and
>    license.
> 2. QEMU already has interfaces to export the vmstate and block device
>    snapshots: migration/savevm and BlockDriverState (NBD for IPC or
>    raw/qcow2/vmdk for file).  It is not necessary to add a
>    special-purpose interface just for backup.
> 
> 3. The backup block job can be composed together with other QMP commands
>    to achieve scenarios besides just VMA backup.  It's more flexible to
>    add simple primitives that can be combined instead of adding a
>    monolithic backup command.
> 
> For these reasons, I'm against putting backup archive code into QEMU.

That is OK for me - I already maintain the code outside of qemu.