[pve-devel] KVM Live Backup performance

[Dietmar Maurer]

> >>The tests form Eric only do reads (there is no single write involved).
> Oh, I miss that.
> 
> I think it should be a qemu problem, as only difference is that
> 
>  with lvm snapshot backup,
> 
> backup reads are done directly from disk
> 
> and with qemu backup
> 
> reads are done through qemu
> 
> Maybe qemu has more overhead to read disk, or maybe they are some
> slowdown when guest need to read disk, and backup job need to read it too.

There is also a small possibility that we have a bug ;-) I will debug that
when I update that code for 1.7.

Looking at the code, it seems that we also backup read blocks immediately. That way we
can avoid re-reads. 

I am not sure if that is good or bad.