Re: [Qemu-block] dirty bitmap restore procedure

[Michael Ablassmeier]

hi again,

On Tue, Nov 29, 2016 at 01:25:42PM -0500, John Snow wrote:
> I hope I have made this clearer instead of more confusing!
> 
> If you'd like to see examples of how we test the incremental backup
> features, take a look at iotest 124 in the QEMU source tree:
> 
> https://github.com/qemu/qemu/blob/master/tests/qemu-iotests/124

giving it another shot i managed to do what i had in mind. The crux was
that i was missing the qemu-img option -u for a lazy rebase because at
all time in my tests i assumed that the full backing image is not
available as i create the incremental backup.

So it went with those steps:

 1) create bitmap/snapshot in transaction
 2) "backup" my image file by copy assuming a third party sofware
    is backing up.
 3) commit snapshot

do some changes to the filesystem 

 1) backup INC using the same bitmap
 2) shutdown vm and delete everything

"restoring" i went by:

 1) copy files from backup
 2) qemu-img rebase -b FULL.img INC.img -u
 3) qemu-img commit INC.img

after bootup vm fs now shows all changes after snapshot
and between snapshot and incremntal backup. 

your input is very appreciated, thanks for your fast
replies john! If all that makes sense i will do a
short writeup with some examples.

bye,
    - michael